Relevance of Static and Dynamic Recrystallizations on Austenite Grain Refinement in Nb-Mo Microalloyed Steels

摘要

The availability of dynamic recrystallization (DRX) as a mechanism for grain refinement for Nb-Mo steels in Thin Slab Direct Rolling (TSDR) processes was studied. Continuous torsion tests were carried out with a 0.034%Nb-0.31%Mo microalloyed steel at deformation conditions similar to those applied in the first rolling passes of TSDR processes. The microstructural evolution of DRX was characterized from specimens quenched after different levels of deformation. It was found that the evolution of DRX was highly heterogeneous, leading to the presence of wide unrecrystallized areas at high values of DRX fraction. Additionally, the results showed that, due to the combined effect of Nb and Mo in solid solution, very high strain levels were required to obtain a significant amount of DRX fraction.