MCQ
641. Tensile strength of steel can be safely increased by--
adding carbon up to 2.8%
adding carbon up to 6.3%
adding carbon up to 0.83%
adding small quantities of copper
642. The toughness of a material --when it is heated.
increases
remain same
decrease
none
643. Surveying tapes are made of a material having low coefficient of expansion and enough strength. The alloy used is—
silver metal
duralumin
Hastelloy
Invar
644. Copper when alloyed with zinc is known as--
Brass
Babbits
Bronze
All of the above
645. In which forging is possible without any problem?
alloy steel
low carbon
high carbon
cast
646. Brass contains--
70% copper and 30% zinc
90% copper and 10% tin
85-92% copper and rest tin with little lead and nickel
70-75% copper and rest tin
647. The lower critical point for all steels is—
600°C
700°C
723°C
913°C
648. The percentage of carbon in pig iron varies from--
0.1 to 12%
2.5 to 4.5%
1.5 to 2.5%
4 to 4.5%
649. The machinability of steel is increased by--
silicon and sulphur
phosphorous, lead and sulphur
sulphur, graphite and aluminium
phosphorous and aluminium
650. Discontinous chips are formed during machining of--
brittle metal
hard metal
ductile metal
soft metal
651. Lead is poured into the joint between two pipes. These pipes may be made of--
cast iron
asbestos cement
vitrified clay
concrete
652. Which of the following iron exists between Type equation here.910°C and 1403°C?
∝-iron
δ -iron
β-iron
γ-iron
653. Pearlite is a combination of--
ferrite and cementite
cementite and gamma iron
ferrite and austenite
ferrite and iron graphite
654. Which of the following material has maximum ductility?
Mild steel
Nickel
Copper
Aluminum
655. The most effective inhibitor of grain growth. when added in small quantities is--
carbon
manganese
vanadium
Cobalt
656. Vanadium in high speed steels--
promotes decarburisation
provides high hot hardness
forms very hard carbides and thus increases wear resistance
promotes retention of austenite
657. Recrystallisation temperature can belowered by--
purification of metal
grain refinement
working at lower temperature
all of the above
658. The percentage of carbon in grey iron castings usually varies between-
0.5 to 1%
2.5 to 4.5%
1 to 2%
5 to 7%
659. The cutting tools are made from--
nickel steel
silicon steel
chrome steel
high speed steel
660. Which of the following element results in presence of free graphite in CI--
carbon
silicon
sulphur
manganese