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Mechanical Engineering Objective Questions { Material Science }



99. The hardness of steel increases if it contains
A.Austenite
B.Martensite
C.Pearlite
D.Cementite

100. Grey cast iron
A.Contains 1.7 to 3.5% carbon in free state and is obtained by the slow cooling of molten cast iron
B.Is also known as chilled cast iron and is obtained by cooling rapidly. It is almost unmachinable
C.Is produced by annealing process. It is soft, tough and easily machined metal
D.Is produced by small additions of magnesium (or cerium) in the ladle. Graphite is in nodular or spheroidal form and is well dispersed throughout the material

101. Nodular iron has
A.High machinability
B.High tensile strength
C.Good fluidity
D.All of the above

102. Nickel in steel
A.Improves wear resistance, cutting ability and toughness
B.Refines grain size and produces less tendency to carburisation, improves corrosion and heat resistant properties
C.Improves cutting ability and reduces hardenability
D.Gives ductility, toughness, tensile strength and anticorrosion properties

103. Which of the following elements does not impart hardness to steel
A.Copper
B.Chromium
C.Nickel
D.Silicon

104. The presence of Sulphur in pig iron makes
A.It easily machinable
B.It brittle
C.It hard
D.The casting unsound

105. Melting point of iron is
A.1539C
B.1601C
C.1489C
D.1712C

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