Recrystallization temperature is one________________?
(A) at which crystals first start forming from molten metal when it is cooled
(B) at which new spherical crystals first begin to form from the old deformed one when a strained metal is heated
(C) at which change of allotropic form takes place
(D) at which crystals grow bigger in size
(D) at which crystals are destroyed on heating
Delta iron occurs at temperature of_______________?
(A) room temperature
(B) above melting point
(C) between 1400°C and 1539°C
(D) between 910°C and 1400°C
(D) none of the above
Super conduction by metals is observed in the temperature range of_________________?
(A) below 10°K
(B) above 100°K
(C) around 0°C
(D) around 100°C
(D) above 1000°C
Which of the following represents the allotropic forms of iron__________________?
(A) alpha iron, beta iron and gamma iron
(B) alpha iron and beta iron
(C) body centred cubic a-iron and face centred cubic a-iron
(D) alpha iron, gamma from and delta iron
(D) none of the above
Gamma iron exits at following temperature___________________?
(A) room temperature
(B) near melting point
(C) between 1400°C and 1539°C
(D) between 910°C and 1400°C
(D) none of the above
Which of the following elements does not impart hardness to steel__________________?
(A) copper
(B) chromium
(C) nickel
(D) silicon
(D) none of the above
Nodular iron has____________________?
(A) high maehinability
(B) low melting point
(C) high tensile strength
(D) good fluidity
(D) all of the above
The hardness of steel increases if it contains____________________?
(A) austenite
(B) martensite
(C) pearlite
(D) cementite
(D) all of the above
Cobalt in steel __________________?
(A) improves wear resistance, cuttinability and toughness
(B) refines grain size and produces les tendency to carburisation, improve corrosion and heat resistant proper ties
(C) improves cutting ability and reduce hardenability
(D) gives ductility, toughness, tensile strength and anti corrosion property:
(D) none of the above