Simulation of the controlled rolling and accelerated cooling of a bainitic steel using torsion testing

Controlled rolling, followed by accelerated cooling, was simulated by means of torsion tests. Nigh-strength low-alloy (HSLA) low-carbon (0.08%) bainitic steel containing B, recently developed by the industry as a bainitic steel grade of the API X80 class, was examined. The influence of cooling rate and finish-cooling temperature on the microstructure and mechanical properties were studied. The final microstructure was predominantly bainitic. For a finish-cooling temperature of 400 degrees C the microstructure consists of fine laths of bainitic ferrite with interlath MA constituent, and increase in the cooling rate leads to a continuous increase of the tensile and yield strengths of 158 and 183 MPa, respectively. The analysis of the results enabled the establishment of quantitative relationships between the accelerated cooling variables and the mechanical properties of steel. (C) 2000 Elsevier Science S.A. All rights reserved.