By simulation of hot rolling using torsion tests and subsequent graphic representation of mean flow stress (MFS) versusthe inverse of temperature for each pass, no-recrystallization temperature (T_nr) was determined for a low niobium microalloyed steel at different interpass times and two strains of 0.20 and 0.35. Recrystallized fraction (X_a) 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: T_nr, the residual stress accumulated in the austenite just before the γ→α transformation (Δσ_r), 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 T_nr and Δσ_r were rather high. However, greater strains and interpass times brought about very small values of T_nr and Δσ_r. In addition to this, new aspects about the definition of T_nr are also discussed in this paper.