contains 1.7 to 3.5% carbon in free state and is obtained by the slow cooling of molten cast iron
is also known as chilled cast iron am is obtained by cooling rapidly. It i: almost unmachinable
is produced by annealing process. I is soft, tough and easily machinec metal
is produced by small additions o magnesium (or cerium) in the ladle Graphite is in nodular or spheroida form and is well dispersed throughout the material
none of the above is true.
Correct answer: (A) contains 1.7 to 3.5% carbon in free state and is obtained by the slow cooling of molten cast iron
73. Gun metal contains
70% copper and 30% zinc
90% copper and 10% tin
85-92% copper and rest tin with little lead and nickel
70-78% copper and rest tin
85-92% copper and rest zinc.
Correct answer: (C) 85-92% copper and rest tin with little lead and nickel
74. Hardness of lower bainite (tempered martensite) is about
RC 65
RC 48
RC 57
RC 80
RC 32.
Correct answer: (C) RC 57
75. Hardness of martensite is about
RC 65
RC 48
RC 57
RC 80
RC 32.
Correct answer: (A) RC 65
76. Hardness of steel depends on
amount of carbon it contains
the shape and distribution of the car-bides in iron
method of fabrication
contents of alloying elements
the quality of ore from which it is made.
Correct answer: (B) the shape and distribution of the car-bides in iron
77. Hardness of upper bainite (acicular structure) is about
RC 65
RC 48
RC 57
RC 80
RC 32.
Correct answer: (B) RC 48
78. Heavy duty leaf and coil spring* contain carbon of the following order
0.2%
0.5%
0.8%
1.0%
1.5%.
Correct answer: (D) 1.0%
79. High carbon steel carries carbon %age c
0.1 to 0.3%
0.3 to 0.6%
0.6 to 0.8%
0.8 to 1.5%
1.5 to 2.5%.
Correct answer: (D) 0.8 to 1.5%
80. If a refractory contains high content of silicon, it means refractory is