Mechanical properties of TMCP Q690 high strength structural steel at elevated temperatures

Abstract

The mechanical properties of high strength structural steel (HSSS) at elevated temperatures are the basis for fire-resistant design of HSSS members and structures. Previous studies on the mechanical properties of HSSS at elevated temperatures were mainly conducted on QT (Quenched and Tempered) HSSS, while few studies were conducted on TMCP (Thermo-Mechanical Controlled Process) HSSS. In order to identify the effect of manufacturing process on the mechanical properties of HSSS at elevated temperatures, an experimental study was carried out by steady-state method on TMCP Q690 HSSS, considering nine elevated temperatures ranging from 200 to 800 °C. Results showed that the elastic modulus and strength of TMCP Q690 HSSS decreased significantly as the temperature increased over 400 °C, while the ultimate elongation increased as the temperature increased above 500 °C. Formulas for calculating the reduction factors of mechanical properties of TMCP Q690 HSSS at elevated temperatures were proposed. Comparing the results of TMCP Q690 HSSS with those of QT Q690 HSSS previously studied, it can be found that the reduction on elastic modulus and strength was more severe for TMCP Q690 HSSS than QT Q690 HSSS in most cases, which was explained in the microstructure level of HSSS.