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Isothernal Transformation Curve

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 austentite has occurred. By taking anumbet of speciments of the same steel and treating them in the same way, but varying the holding temperature and time 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.