Engineering Materials
Points of arrest for iron correspond to

Stages at which allotropic forms change
Stages at which properties do not change with increase in temperature
There is nothing like points of arrest
Stages at which further heating does not increase temperature for some time

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

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