The high-temperature deformation behaviors of low and medium carbon steels with respectively 0.06 and 0.5 wt% C were investigated under strain rate and temperature ranges of 10-4–10-1 s-1 and of 900–1100 °C. Three types of dynamic recrystallization (DRX) flow behaviors were identified, namely single peak, multiple transient steady state (MTSS), and cyclic behaviors. The normalized critical stress (and strain) for the low and medium carbon steels were about 0.846 (0.531) and 0.879 (0.537), respectively. For both steels, the apparent deformation activation energy and the power of the hyperbolic sine law were found to be near the lattice self-diffusion activation energy of austenite (270 kJ/mol) and 4.5, respectively. As a result, it was concluded that the flow stress of plain carbon steels in hot deformation is mainly controlled by dislocation climb during their intragranular motion, and based on physically-based constitutive analysis, it was found that carbon has a slight effect on the hot flow stress of plain carbon steels. The significance of the approach used in this work was shown to be its reliance on the theoretical analysis based on the deformation mechanisms, which makes the comparison more reliable.

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