MCQs on Fundamentals of Casting
1 - Question
If we decrease the freezing range, then the fluidity of metal will?
c) Will not change
d) Initially increase and then decrease
Explanation: Fluidity is inversely proportional to the freezing range. Thus, the shorter the range (as in pure metals and eutectics), the higher the fluidity becomes. Conversely, alloys with long freezing ranges (such as solid-solution alloys) have lower fluidity.
2 - Question
According to Chvorinov’s rule the solidification time is a function of volume and surface area and is given by the relationship between volume, area and some exponential power ‘n’. What is the value of n?
Explanation: Chvorinov’s rule states that: ts = B×(VA)n, where ts is the time of solidification, v = volume, A = surface area, n = 1.5 to 2 and B is a constant for metal cast, mold material and casting conditions.
3 - Question
Which one of the following expands during solidification?
a) Mild steel
b) Grey cast iron
Explanation: Grey cast iron expands upon solidification, as graphite has a relatively high specific volume and it precipitates as graphite flakes during solidification, it causes a net expansion of the metal. advertisement
4 - Question
Dissolved gases may be removed from molten metal by?
a) Flushing or purging with inert gas
b) Melting and pouring the metal in vacuum
c) Flushing or purging with inert gas or Melting and pouring the metal in vacuum
d) Melting and pouring the metal in nitrogen atmosphere
Explanation: Dissolved gases may be removed from molten metal either by flushing or purging with inert gas or melting and pouring the metal in vacuum.
5 - Question
Doubling the time in flat mould will increase the thickness of wall skin by what percentage?
Explanation: Thickness is proportional to √ time. When time is doubled in flat mould, thickness of wall skin will increase by 41%.
6 - Question
Solidification of casting does not depend upon which factor?
a) Type of metal
b) Thermal properties of metal
c) Geometric relationship between volume and surface area
d) Surface tension
Explanation: Surface tension is a fluid property and solidification time of casting does not depend upon any fluid property.
7 - Question
The following characteristic of molten metal influence the fluidity. i) Mushy zone ii) Viscosity iii) Surface tension iv) Inclusion Which one of the following is correct?
a) i and ii
b) i only
c) i, ii and iii
d) i, ii, iii and iv
Explanation: All the above mention characteristics influence fluidity. Fluidity in casting is used to designate the casting material ability to fill the mould cavity.
8 - Question
What is the function of cores used in casting?
a) To remove dissolved gases
b) To avoid defects
c) To form hollow region
d) To reduce shrinkage porosity
Explanation: Cores form internal cavities inside the structure which will then leads to the final casting shape with hollow structure. Sand inside cores and pattern gives strength and rigidity to the casting structure.
9 - Question
Which one of the statements is not correct in metal casting?
a) Rapid cooling produces a solidified skin or shell
b) Those grain that have favourable orientation will grow preferentially
c) Cast iron has wide mushy zones
d) Lack of uniformity in grains size and distribution will cause anisotropic properties
Explanation: Cast iron has low range of mushy zone. Rapid cooling produces a solidified skin or shell and Lack of uniformity in grains size and distribution will cause anisotropic properties.
10 - Question
Assertion (A): Chills are used to reduce shrinkage porosity. Reason (R): the function of chill is to increase the rate of solidification in a critical region.
a) Both A and R is correct, and R is a correct explanation for A
b) Both A and R is correct, and R is an incorrect explanation for A
c) A is wrong but R is correct
d) A is correct but R is wrong
Explanation: Chills are used to reduce shrinkage porosity and the function of chill is to increase the rate of solidification in critical region.