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 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

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Engineering Materials
Smelting is the process of

Reducing the ore with carbon in the presence of a flux
All of these
Expelling moisture, carbon dioxide, sulphur and arsenic from the iron ore by heating in shallow kilns
Removing the impurities like clay, sand etc. from the iron ore by washing with water

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Engineering Materials
Cyaniding is the process of

Adding carbon and nitrogen by heat treatment of steel to increase its surface hardness
Obtaining cyanide salts
Dipping steel in cyanide bath
Reacting steel surface with cyanide salts

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Engineering Materials
The brown smoke during the operation of a Bessemer converter indicates that the

Air is burning out silicon and manganese
The brown smoke does not occur during the operation of a Bessemer converter
Silicon and manganese has burnt and carbon has started oxidizing
The converter must be titled to remove the contents of the converter

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