<p>In order to improve the mechanical properties of ferritic stainless steel, this study investigates the effects of Nb microalloying (0–0.2 wt.%) on Cr13 stainless steel. The results reveal that Nb additions modify phase composition and grain morphology. Columnar grains transform into equiaxed grains with abnormal coarsening, while Cr/C-rich precipitates convert to Nb(C, N) phases. Tensile properties indicate that compared with Cr13 stainless steel (348 MPa-7.4%), the ultimate tensile strength of Cr13–0.2Nb stainless steel decreases slightly to 322 MPa, while plastic extension significantly improves to 16.1%. This enhancement originates from the formation of Nb(C, N) phases suppressing brittle Cr/C-rich precipitates, thereby improving the ductility. Furthermore, the precipitate phase transformation improves the impact properties of Cr13 stainless steels. Low-temperature impact energy increases from 2.71 J/cm² (Cr13) to 4.57 J/cm² (Cr13–0.2Nb). Tensile fracture transitions from mixed cleavage-dimple mode to the ductile. The addition of Nb enhances plasticity and impact toughness primarily by reducing brittle Precipitate-A and promoting coarser Precipitate-B and grain growth, which alleviates dislocation pinning and stress concentration. Through investigating the effects of precipitates on the microstructure, microhardness and tensile properties of Cr13 stainless steels, this study provides crucial experimental data and theoretical foundations for optimizing composition design and developing high-quality ferritic stainless steels.</p>