Physical Metallurgy Related to the Thermomechanical Process of Hot Rolling of Nb Microalloyed Steel Beams: Prediction of Mechanical Properties

The main physical metallurgy processes controlling final mechanical properties in as hot rolled steel products are basically recrystalization, grain growth, precipitation and austenite to ferrite phase transformation. Knowledge of how these processes interact during an industry hot rolling schedule is the key to understand how to obtain certain mechanical properties. This know how has been routinely applied to the manufacturing of flat products such as plates and strips. Less has been reported for non flat products. When even there are such reports, these usually do not present any comparison between predictions and industry real data. This paper addresses the case of rolling of structural beams at an industry trial. Emphasis is put on how the final mechanical properties were obtained and how they can be predicted. An ordinary microstructure model was used and then the predictions were checked by comparing them to industry data. After validation, suggestions were made for improvements in the schedule aiming at having superior mechanical properties at the end product. Austenite grain size evolution is important in defining final properties, as expected. The presence of Nb as microalloyed element can enhance such properties and its role to this particular industry process was discussed.