Present work deals with the study of structural changes of a medium carbon microalloyed steel during two heat treatment cycles as isothermal transformation and thermo mechanical processing followed by isothermal processing In isothermal transformations, the steel immediately after austenitization at 1250 deg C for 20 minutes was transferred a to salt bath at a preselected temperature of 365, 400, 435, 470 or 500 deg C and after holding for 35 minutes followed by their quenching in water. In the other heat treatment cycle, after austenitization at 1250 deg C for 20 minutes the steel was subjected to thermomechanical treatment by hot rolling at a finish temperature of 750 deg C followed by isothermal treatment under the similar conditions as mentioned above. The structural changes during the two type of processing have been investigated using optical microscopy and X-ray diffraction technique. The effect of isothermal treatment temperature on the hardness, UTS, percent Elongation and Toughness of steel processed by these two processing routes have also been studied and related to their microstructures.
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