Transformation of iron carbide into graphite (graphitization) was observed to occur during industrial processing of high carbon thin strip steel. Samples of cold rolled and isothermally annealed steels (AISI types 1075 and 1095) were taken along their processing route and were subjected to a series of isothermal annealing treatments in the temperature range of 560–680°C for periods of time ranging from 20 to 500 h. The structures of the different samples were those of cold rolling (spheroidized carbides within a deformed ferritic matrix) and subcritical annealing (spheroidized carbides in undeformed ferrite). It was found that the rate of graphitization depends on the type of steel and degree of deformation. No graphite was found in samples from the lower carbon steel which were subcritically annealed, although they were observed in specimens from the other steel which were cold rolled to a reduction of 50% prior to the subcritical annealing.