Question

5. a) A sample of eutectoid steel is continuously cooled at a rate of 25C/s. What microstructure do you expect to form?

b) Process (a) is repeated for 4340 steel. What microstructure forms in this case?

Answer 1

5(a) the carbon percentage in eutectoid steel in 0.8 % , so coarse or fine pearlite ill form depending upon the

cooling rate .

and since the cooling rate is 25 C/s which is low so the final microstructure will be coarse pearlite with about 88% alfa iron and 12 % cementite

5(b) carbon percentage in 4340 steel is 0.4 %, and for the same cooling rate here also coarse pearlite ill form ith alfa iron percentage = (6.67-.4)/(6.67-.02) = 0.9428, that is 94.28% alfa phase and 5.71 % cemetite