Motivated by inconsistencies in low-temperature toughness of nominally identical hot-rolled high-strength, low-alloy (X65-80) strip, the present study utilizes Gleeble hot torsion simulation to examine thermomechanical processing effects. Recrystallization characteristics of rolled and simulated microstructures were compared using electron backscatter diffrac-tion, with specific toughness-relevant texture components isolated from resultant orientation distribution function maps. Given the importance of controlling austenite recrystallization, temperature ranges for full, partial and negligible recrystalli-zation were measured using double-twist Gleeble testing. After establishing baseline ranges for fully annealed material, the accumulated effects of hot rolling passes were examined through iteratively incorporating reduction passes prior to subsequent double-twist testing.

Hot-rolled microalloyed steels present heat treatment challenges due to alloy segregation and recrystallization tendencies. Normalizing can minimize these effects and promote the desired microstructure and mechanical properties. This study evaluated four normalizing strategies for round bars to optimize cycle times for the production requirements. It includes single normalization, double normalization, extended normalization and an in-line furnace pulsing approach. After nor-malizing, the bars were quenched and tempered, and their mechanical properties were assessed against customer speci-fications. The findings from this study provide guidance on selecting appropriate processing routes to achieve a balanced combination of microstructure and mechanical properties in round bars. 

Hot-rolled plates for API X80 pipes were developed at Gerdau Ouro Branco. A special steel design was adopted in terms of chemical composition and rolling schedule in order to comply with a strict pipe specification, demanding the simultaneous compliance to tensile requirements in the as-rolled condition and after simulated postweld heat treatment, in both trans-verse and longitudinal directions. After rolling, samples were taken for mechanical and microstructural characterization. Microstructural evolution of austenite during rolling was simulated via mathematical models for the assessment of precipi-tation behavior. The plates were then shipped to the customer for pipe forming.
 

A low-carbon titanium-microalloyed chemistry was selected for the development of hot-rolled galvanized high-strength high-formable steel with minimum yield strength of 550 MPa through an Endless Strip Processing production facility. A clean steel practice combined with a suitable choice of hot rolling and galvanizing practice was optimized to retain precipi-tate strengthening in the final fully processed steel and microstructural attributes that resulted in superior forming charac-teristics. In this article, production strategy and advanced material characterization of high-strength, low-alloy steels with minimum yield strength of 550 MPa will be discussed, and results will be presented.