The lower critical point, i.e. 723°C, is denoted as A\ and marks the
transformation from a ferrite-plus-pearlite structure to one of ferrite-plus-
austenite. The upper critical point is denoted as A
3
and marks the transform-
ation from a ferrite-plus-austenite structure to one of just austenite.
For a hypereutectoid steel the lower critical point A
\
marks the transform-
ation from a steel with a structure of pearlite plus cementite to one of austenite
plus cementite. The upper critical point marks the transformation from the
austenite-plus-cementite structure to austenite and is denoted by A
cm
.
Cooling curve ...
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