adding carbon and nitrogen by heat treatment of steel to increase its surface hardness
obtaining cyanide salts
making corrosion resistant steel.
Correct answer: (C) adding carbon and nitrogen by heat treatment of steel to increase its surface hardness
53. Delta iron occurs at temperature of
room temperature
above melting point
between 1400°C and 1539°C
between 910°C and 1400°C
none of the above.
Correct answer: (C) between 1400°C and 1539°C
54. Delta metal is an alloy of
copper, zinc and iron
iron, nickel and copper
iron, lead and tin
iron, aluminium and magnesium
copper, zinc and antimony.
Correct answer: (A) copper, zinc and iron
55. Depth of hardness of steel is increased by addition of
nickel
chromium
tungsten
vanadium
ell of the above.
Correct answer: (B) chromium
56. Dislocations in materials refer to the following type of defect
point defect
line defect
plane defect
volumetric defect
chemical defect.
Correct answer: (B) line defect
57. Dow metal contains
94% aluminium, 4% copper and 0.5% Mn, Mg, Si and Fe
92.5% aluminium and, 4% copper, 2% nickel and 1.5% Mg
90% aluminium and 90% copper
90% magnesium and 9% aluminium with some copper
90% magnesium and 10% tin.
Correct answer: (D) 90% magnesium and 9% aluminium with some copper
58. Drop forging dies contain carbon of the order of
0.1 to 0.2%
0.25 to 0.5%
0.6 to 0.7%
0.7 to 0.9%
1.0 to 1.2%.
Correct answer: (C) 0.6 to 0.7%
59. Ductile cast iron
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 and is obtained by cooling rapidly. It is almost unmachinable
is produced by annealing process. It is soft, tough and easily machined metal
is produced by small additions of magnesium (or creium) in the ladle. Graphite is in nodular or spheroidal form and is well dispersed throughout the material
none of the above.
Correct answer: (D) is produced by small additions of magnesium (or creium) in the ladle. Graphite is in nodular or spheroidal form and is well dispersed throughout the material
60. Ductility of a material can be defined as
ability to undergo large permanent deformations in compression
ability to recover its original form
ability to undergo large permanent deformations in tension
all of the above
none of the above.
Correct answer: (C) ability to undergo large permanent deformations in tension