I would really appreciate your help in parts d, c and f. I am not sure how to do
ID: 1710227 • Letter: I
Question
I would really appreciate your help in parts d, c and f. I am not sure how to do the calculations for c and d.
a) Carbon content of 1040 steel, hypoeutectoid or hypereuctectoid?
b) What would happen if steel were cooled under equilibrium coniditons from 900 degrees C?
c) % wt content of eutectoid phase is material is cooled slowly? (annotate phase diagram)
d) Composition of the steel if quenched rapidly after cooling to 740 degrees C? (annotate the phase diagram)
e) What influences the hardness of the pearlite phase?
f)What is the maximum hardness material that can be made from 1040 steel using a simple heat
and quench process and explain in detail how you would manufacture it
Explanation / Answer
C) The lower limit of single phase solid field formed by two falling phase boundaries intersecting in a V is called eutectoid point.At 0.8 wt %C a eutectoid point will be formed .
Eutectoid Point
First consider the Fe-C phase diagram below 1000ºC, up to
2.0wt% carbon (shown in expanded view in Figure 15). This
shows the low solubility of carbon in ferrite, with a maximum of
0.035wt% at 723ºC. Below the transformation temperature of
ferrite to austenite (910ºC) the picture resembles the partition
behaviour seen below the melting point of a pure element, with
two phase boundaries falling from this temperature and a two-
phase region in between. But in this case the upper phase is a
solid solution (austenite), rather than a liquid. But at the
temperature of maximum C solubility in ferrite (723ºC), the
lower limit of the austenite field also forms a “V”, giving the
minimum temperature at which austenite forms as a single phase,
at a composition of 0.8wt% C.
This feature on a phase diagram is called a eutectoid point, and is
particularly important in the context of carbon steels (as
illustrated later when we consider their microstructures and heat
treatments). Note the similarity in shape to a eutectic, with the
key difference that the phase above the “V” is a single solid phase
(as opposed to a single liquid phase in the case of a eutectic).