By simulation of hot rolling using torsion tests and subsequent graphic representation of mean flow stress (MFS) versus the inverse of temperature for each pass, no-recrystallization temperature (Tnr) was determined for a low niobium microalloyed steel at different interpass times and two strains of 0.20 and 0.35. Recrystallized fraction (Xa) against time curves and RPTT diagrams were also determined for these two strains. This work has allowed evaluation of the influence of a very low Nb content on three aspects: Tnr, the residual stress accumulated in the austenite just before the γ→α transformation (Δσr), and recrystallization-precipitation interaction. It was found that when the strain applied was 0.2 and the interpass times were less than 30 s, the values of Tnr and Δσr were rather high. However, greater strains and interpass times brought about very small values of Tnr and Δσr. In addition to this, new aspects about the definition of Tnr are also discussed in this paper.