a) and b) correct - Incorrect, whilst a) is correct it is not necessary to have a high temperature to create a carbon atmosphere (for example charcoal is stable at room temperature). Try again.
a) and b) and c) correct - Incorrect, whilst a) is correct it is not necessary to have a high temperature to create a carbon atmosphere (for example charcoal is stable at room temperature). Also the diffusivity of carbon is lowered as the temperature is reduced however it is an interstitial element and therefore it is able to diffuse effectively at room temperature. Try again.
a) and d) correct - Correct.
a) and d) correct - Incorrect, whilst d) is correct it is not necessary to have a high temperature to create a carbon atmosphere (for example charcoal is stable at room temperature). Try again.
all correct - Incorrect, whilst a) and d) are correct it is not necessary to have a high temperature to create a carbon atmosphere (for example charcoal is stable at room temperature). Also the diffusivity of carbon is lowered as the temperature is reduced however it is an interstitial element and therefore it is able to diffuse effectively at room temperature. Try again.
Try again.
Click on your answer to check and make a note of the answer on your notepad.
If you have not already reviewed the section on carburising do
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NOTEPAD
Well done!
a) The diffusivity of carbon increases with an increase
in temperature therefore making it more economical (i.e. shorter
times) to carburise at high temperatures. b) To obtain a carbon atmosphere a high temperature
is required. c) Diffusivities of carbon are too low at low temperatures. d) The solubility of carbon in ferrite is too low to
allow any appreciable increase in carbon concentration in
the steel.
Why is carburising carried out at high temperatures? Click on the possible answers to check.
a) and b) correct - Incorrect, whilst a) is correct it is not necessary to have a high temperature to create a carbon atmosphere (for example charcoal is stable at room temperature). Try again.
a) and d) correct - Correct.
