Effects of corrosion on post-fire mechanical properties of Q690 high-strength steel

To explore the mechanical properties of high-strength steel subjected to different corrosion effects, this study conducts experiments on the mechanical properties of Q690 steel after both corrosion and high-temperature exposure. A total of 120 specimens are designed to be first corroded to target corrosion levels and then heated to predetermined temperatures. Subsequently, tensile test is conducted to obtain the mechanical properties. In addition, the surface morphology of specimens is assessed using a 3D scanner. The test results reveal that heat treatment degrades yield strength and ultimate strength while enhancing ductility in uncorroded Q690 steel after experiencing temperatures above 600 degrees C. For Q690 steel corroded over 10 %, corrosion accelerates the degeneration of these strength properties, starting at 400 degrees C, and partially offsets the improvement in ductility. To evaluate the interaction effect between corrosion and fire on the mechanical properties of Q690 steel, an interaction coefficient is proposed, which demonstrates that this interaction has a minor positive influence on the mechanical properties at lower temperatures, while additional adverse influence reaches approximately 10 % from 500 degrees C to 700 degrees C. This interaction is strongly correlated with the surface roughness that rises with increased corrosion duration and temperature. Based on the test results, the stress-strain curves are well-calibrated, providing effective approaches to predict the mechanical behavior of corroded high-strength steel components after a fire.