Effect of Niobium on the Recrystallization, Texture, and Impact Toughness of Hot-Rolled Ferritic Stainless Steels

The present work discusses the impact of different niobium (Nb) additions on the microstructure evolution and toughness of two conventional Nb-stabilized ferritic stainless steel produced under different hot rolling conditions in a lab-scale mill (FENN). The microstructure was investigated using EBSD/SEM to assess recrystallization, texture development, and grain boundary character distribution (GBCD). The results provided an important perspective of the effect of Nb in solid solution on delaying recrystallization and reducing the fractions of recovery in samples that were rolled at lower temperatures, where enough driving force was expected for recrystallization to occur. As a result, a finer and more homogenous microstructure could be reached in the high-Nb concept, providing preferential conditions for better performance in V-Notch Charpy tests of such grades. Finally, the high-Nb grade also presented higher fractions of γ -fiber in the controlled hot rolling conditions with Zener–Hollomon parameter and interpass time optimized. The substantial improvement in the toughness of these ferritic grades opens the possibility of replacing conventional carbon steels in various applications within the capital goods market and creating competitive advantages in terms of cost, formability, and specific properties for certain industrial segments.