Observation of Recrystallization Behavior of Nb-Microalloyed Wide Flange Beams during Hot-Rolling

Abstract

Nb-microalloying has a significant effect on microstructure evolution during hot-rolling. Metallurgical benefits of niobium are associated with the formation of Nb(C, N) in ferrite and austenite, retardation of austenite recrystallization , and further austenite to ferrite phase transformation. Precipitation and microstructure control are therefore important features to achieve better strength and toughness simultaneously. Effects of hot-rolling conditions on strength and toughness are of great interest because the rolling parameters, e.g., temperature, roll force, and cooling rate, contribute to strengthening mechanism of Nb-microalloyed steels. Grain refinement is the most practical way to enhance the niobium -bearing steels by strain-induced precipitation hardening below the non-recrystallization temperature . This rolling research involves residual stress variation associated with parallel-flange section geometry. Therefore, a repetitive hardening–softening mechanism could be an important feature to predict the final mechanical properties . Computational and experimental analysis has been used to determine flow stress according to the temperature change in hot-rolling. The recrystallization behavior is experimentally observed through the multiple rolling .