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
Cobalt in steel

Gives ductility, toughness, tensile strength and anti corrosion property
Improves wear resistance, cutting ability and toughness
Improves cutting ability and reduce hardenability
Refines grain size and produces less tendency to carburisation, improve corrosion and heat resistant proper ties

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Engineering Materials
Grey cast iron

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

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