Engineering Materials

151. The metallic structure of mild steel is

  1. body centred cubic
  2. face centred cubic
  3. hexagonal close packed
  4. cubic structure
  5. orthorhombic crystal.

Correct answer: (A)
body centred cubic

152. The molecules in a solid move

  1. in a random manner
  2. in a haphazard way
  3. in circular motion
  4. back and forth like tiny pendulums
  5. do not move.

Correct answer: (D)
back and forth like tiny pendulums

153. The most effective inhibitor of grain growth, when added in small quantities is

  1. carbon
  2. vanadium
  3. manganese
  4. cobalt
  5. copper.

Correct answer: (B)
vanadium

154. The number of electrons in 1 cm3 of metal would be of the order of

  1. 1010
  2. TO16
  3. 1022
  4. 1040
  5. 1052

Correct answer: (C)
1022

155. The percentage of carbon in grey iron castings usually varies between

  1. 0.5 to 1%
  2. 1 - 2%
  3. 2.5 to 4.5%
  4. 5 - 7%
  5. 7-9%.

Correct answer: (C)
2.5 to 4.5%

156. The percentage of carbon in low carbon steel is

  1. 0.05%
  2. 0.15%
  3. 0.3%
  4. 0.5%
  5. 0.7%.

Correct answer: (B)
0.15%

157. The percentage of carbon in pig iron varies from

  1. 0.1 to 1.2%
  2. 1.5 to 2.5%
  3. 2.5 to 4%
  4. 4 to 4.5%
  5. 4.5 to 6.3%.

Correct answer: (D)
4 to 4.5%

158. The presence of sulphur in pig iron makes

  1. it easily machinable
  2. it brittle
  3. it hard
  4. the casting unsound
  5. increases the fluidity.

Correct answer: (D)
the casting unsound

159. The surface hardness of the following order is achieved by nitriding operation

  1. 600 VPN
  2. 1500 VPN
  3. 1000 to 1100 VPN
  4. 250 VPN
  5. 2000 VPN.

Correct answer: (C)
1000 to 1100 VPN

160. The temperature at which ferromagnetic alpha iron transforms to paramagnetic alpha iron is

  1. 770°C
  2. 910°C
  3. 1050°C
  4. below recrystallisation temperature
  5. above recrystallization temperature.

Correct answer: (A)
770°C

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