591. Equal amounts of a liquid metal at the same temperature are poured into three moulds made of steel, copper and aluminum. The shape of the cavity is a cylinder with 15 mm diameter. The size of the moulds are such that the outside temperature of the moulds do not increase appreciably beyond the atmospheric temperature during solidification. The sequence of solidification in the mould from the fastest to slowest is (Thermal conductivities of steel, copper and aluminum are 60.5, 401 and 237 W/mK, respectively. Specific heats of steel, copper and aluminum are 434, 385 and 903 J/ kgK, respectively. Densities of steel, copper and aluminum are 7854, 8933 and 2700 kg/m³, respectively.)

1. 1. Copper - Steel - Aluminium

   
   
   

   2. Aluminum - Steel - Copper

   
   
   

   3. Copper - Aluminium - Steel

   
   
   

   4. Steel-Copper-Aluminum

   
   
   

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1. View Hint View Answer Discuss in Forum

   Solidification time is inversely proportional to diffusivity and based on the values diffusivity is highest for copper, next is aluminium and then steel. Hence the solidification time is lowest for copper, next aluminium and then steel.

   Correct Option: C

   Solidification time is inversely proportional to diffusivity and based on the values diffusivity is highest for copper, next is aluminium and then steel. Hence the solidification time is lowest for copper, next aluminium and then steel.

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592. A cylindrical job with diameter of 200 mm and height of 100 mm is to be cast using modulus method of riser design. Assume that the bottom surface of cylindrical riser does not contribute as cooling surface. If the diameter of the riser is equal to its height, then the height of the riser (in mm) is

1. 1. 150

   
   
   

   2. 200

   
   
   

   3. 100

   
   
   

   4. 125

   
   
   

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1. View Hint View Answer Discuss in Forum

   According to modulus method M_R = 1.2 M_C
   

   	V			= 1.2		V
   	As		R			As		C

   
   If diameter of riser = height of riser for top riser D = H
   ⇒  D = 6 M_C
   

   D = 6 ×	(π/4) × (200)2 × 100
   	2 × (π/4) × (200)2 + π × 200 × 100

   
   

   D = H =	6 × 200 × 100	= 150 mm
   	400 + 400

   Correct Option: A

   According to modulus method M_R = 1.2 M_C
   

   	V			= 1.2		V
   	As		R			As		C

   
   If diameter of riser = height of riser for top riser D = H
   ⇒  D = 6 M_C
   

   D = 6 ×	(π/4) × (200)2 × 100
   	2 × (π/4) × (200)2 + π × 200 × 100

   
   

   D = H =	6 × 200 × 100	= 150 mm
   	400 + 400

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593. The part of a gating system which regulates the rate of pouring of molten metal is

1. 1. pouring basin

   
   
   

   2. runner

   
   
   

   3. choke

   
   
   

   4. ingate

   
   
   

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1. View Hint View Answer Discuss in Forum

   Rate of pouring of molten metal depends on pouring basin.

   Correct Option: A

   Rate of pouring of molten metal depends on pouring basin.

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594. The dimensions of a cylindrical side riser (height = diameter) for a 25 cm × 15 cm × 5 cm steel casting are to be determined. For the tabulated shape factor values given below, diameter of the riser (in cm) is_______.
     Shape Factor    2    4    6    8    10   12
     Riser volume/    1.0    0.70    0.55    0.50    0.40    0.35
     Casting volume

1. 1. 11.60 cm

   
   
   

   2. 10.66cm

   
   
   

   3. 10.60cm

   
   
   

   4. None of the above

   
   
   

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1. View Hint View Answer Discuss in Forum

   Z =	L + W
   	Thickness

   
   

   =	25 + 15	= 8
   	5

   
   

   Riservolume	= 0.5
   Casting volume

   
   

   =	(π/4)d2h	= 0.5
   	25 × 15 × 15

   
   but d = h
   

   πd3	= 0.5 × 25 × 15 × 15
   4

   
   d = 10.60cm

   Correct Option: C

   Z =	L + W
   	Thickness

   
   

   =	25 + 15	= 8
   	5

   
   

   Riservolume	= 0.5
   Casting volume

   
   

   =	(π/4)d2h	= 0.5
   	25 × 15 × 15

   
   but d = h
   

   πd3	= 0.5 × 25 × 15 × 15
   4

   
   d = 10.60cm

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595. Ratio of solidification time of a cylindrical casting (height = radius) of that of a cubic casting of side two times the height of cylindrical casting is_______.

1. 1. 2 : 3

   
   
   

   2. 3 : 4

   
   
   

   3. 1 : 2

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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