Engineering Materials
In a hardening process, the hypo-eutectoid steel is

Heated from 30°C to 50°C above the upper critical temperature and then cooled in still air
Heated below or closes to the lower critical temperature and then cooled slowly
Heated from 30°C to 50°C above the upper critical temperature and then cooled slowly in the furnace
Heated from 30°C to 50°C above the upper critical temperature and then cooled suddenly in a suitable cooling medium

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Engineering Materials
Combined carbon in iron makes the metal

Soft and gives coarse grained crystalline structure
Hard and gives a fine grained crystalline structure
Soft and gives a fine grained crystalline structure
Hard and gives a coarse grained crystalline structure

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Engineering Materials
Steel contains

Alloying elements like chromium, tungsten nickel and copper
50% or more iron
Elements like phosphorus, sulphur and silicon in varying quantities
80% or more iron

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