71. Low permeability moulds and low pouring temp of the molten metal causes blow holes. Defect in castings.(T/F)

1. 1. True

   
   
   

   2. False

   
   
   

   3. NA

   
   
   

   4. NA

   
   
   

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   True

   Correct Option: A

   True

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72. Poor collapsibility of the mould leads to distortion cracks type of casting defect in aluminium castings. (T/F)

1. 1. True

   
   
   

   2. False

   
   
   

   3. NA

   
   
   

   4. NA

   
   
   

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   NA

   Correct Option: C

   NA

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73. The fluidity of molten metal of cast alloys (without any addition of fluxes) increases with increase in

1. 1. freezing range

   
   
   

   2. viscosity

   
   
   

   3. degree of superheat

   
   
   

   4. surface tension

   
   
   

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   NA

   Correct Option: C

   NA

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74. Match the following sand mold casting effects with their respective causes.
    

1. 1. P-3, Q-4, R-1, S-2

   
   
   

   2. P-3, Q-4, R-2, S-1

   
   
   

   3. P-4, Q-3, R-1, S-2

   
   
   

   4. P-2, Q-4, R-1, S-3

   
   
   

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   NA

   Correct Option: C

   NA

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75. The hot tearing in a metal casting is due to

1. 1. high fluidity

   
   
   

   2. high melt temperature

   
   
   

   3. wide range of solidification temperature

   
   
   

   4. low coefficient of thermal expansion

   
   
   

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   NA

   Correct Option: A

   NA

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