Engineering Materials
Ductile cast iron

Is produced by annealing process. It is soft, tough and easily machined metal
Is also known as chilled cast iron and is obtained by cooling rapidly. It is almost unmachinable
Is produced by small additions of magnesium (or creium) in the ladle. Graphite is in nodular or spheroidal form and is well dispersed throughout the material
Contains 1.7 to 3.5% carbon in Free State and is obtained by the slow cooling of molten cast iron

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Engineering Materials
The unit cells

May be defined as the smallest parallelepiped which could be transposed in three coordinate directions to build up the space lattice
Have the same orientation and their similar faces are parallel
All of these
Contain the smallest number of atoms which when taken together have all the properties of the crystals of the particular metal

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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 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
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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