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

Abstract

Controlled rolling, followed by accelerated cooling, was simulated by means of torsion tests. High-strength low-alloy (HSLA) lowcarbon (0.08%) bainitic steel containing B, recently developed by the industry as a bainitic steel grade of the API X80 class, was examined. The in¯uence of cooling rate and ®nish-cooling temperature on the microstructure and mechanical properties were studied. The ®nal microstructure was predominantly bainitic. For a ®nish-cooling temperature of 4008C the microstructure consists of ®ne 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.