This document examines the effect of carbon content on grain refinement in C-Mn and interstitial-free (IF) steels deformed via warm working. Four steels with varying carbon contents were strained at 700°C to 2.3. Dynamic recrystallization resulted in a 2 μm ferrite grain size at the surface for all steels. However, microstructures varied between the center regions based on carbon content, from coarse grains in IF steel to martensite and bainite in the highest carbon steel. Increasing carbon decreased ferrite grain size after deformation but also increased strength, while alloying elements aided additional refinement.