Also known as the Time Temperature
Transformation Curve. If a small piece of steel
is heated sufficiently slowly for it to become
austenitic and then plunged into a salt bath
and held at a constant temperature below the
upper critical point for a definite time followed
by rapid quenching, it is possible by
examination to determine the extent to which
the transformation of the austenite has
occurred. By taking a number of specimens of
the same steel and treating them in the same
way, but varying the holding temperature and
time the behavior of the steel with time and
temperature can be studied. The information
obtained can be plotted as time-temperature
transformation curves which is useful in heat
treatment practice, particularly for
martempering and austempering.