Which of the following alloy steels is the most suitable for making gun barrels and projectiles?

Which of the following is universally employed as the low expansion metal in the bimetallic thermometer, which is an iron-nickel alloy containing 36% nickel and has very low co-efficient of expansion (l/20th of ordinary metals)?

A. Invar

B. Constantan

C. Chromel

D. Alumel

In drop forging process, the forging is done by dropping the __________ at high velocity.

A. Hammer

B. Workpiece

C. Die with hammer

D. Weight on hammer

Most of the common metals have __________ crystal structure.

A. Cubic

B. Hexagonal

C. Orthorhombic

D. None of these

Chrome vanadium steels usually contain 0.8 to 1.1% Cr, 0.25 to 0.35% C and < 0.25% V. It is

A. Used for making axle & shafts of aeroplanes, automobiles and locomotives

B. Having poor fatigue resistance

C. Having poor toughness

D. Not helpful in producing cleaner steel due to oxidising action of vanadium