Diagrams of CT and IT in heat treatment of the steels

Question

Write down the differentiation between diagrams of CT and IT in heat treatment of the steels.

Answer 1

Isothermal Transformation (or IT) as well as Continuous Transformation (or CT) diagrams are diagrams which are employed to investigate kinetic characteristic of phase transformations and are of extensive employ in steels heat treatment. In these sorts of diagrams basically named as Time-Temperature-Transformation (or TTT), the abscissa is time in the logarithmic scale and ordinate is temperature. The C shaped curves point to the onset and the end of the diffusion (civilian) transformations e.g. bainite or pearlite formation or precipitation of the carbides.

IT diagram shows what takes place if steel is held at a constant temperature for the prolonged period. The development of the microstructure with time can be followed through the holding small specimens in a lead or salt bath and extinguishing them one at a time after raising holding times and measuring the amount of the phases formed in the microstructure with the assist of a microscope. An alternative technique involves using the single specimen and the dilatometer that records the elongation of the specimen as function of time. The basis for the dilatometer technique is that the micro constituents undergo dissimilar volumetric alters and thus, the onset of transformations could be perceived.