Elevated temperature tensile behavior of S900 HSLA steel and its welded joints: Fid-Bau Portal

Elevated temperature tensile behavior of S900 HSLA steel and its welded joints

Narimani, M. / Hajjari, E. / Eskandari, M. / Szpunar, J.A.

Abstract Owing to the application of high-strength low-alloy (HSLA) steels and their welded joints in the steel structure of buildings, developing reliable predictive equations for their mechanical properties at elevated temperatures and fire conditions are a matter of great concern. The present study examined the tensile behavior of S900 HSLA steel and its welded joints at elevated temperatures. The steady-state tension tests were conducted at temperatures ranging from 25 to 800 °C. Based on the obtained experimental results, predictive equations for stress-strain curves and reduction in mechanical properties of S900 HSLA and its welded joint were developed. Electron backscattered diffraction (EBSD) was utilized to analyze the microstructure and understand the correlation between the microstructure and the tensile properties. The obtained results revealed that S900 HSLA steel had a higher tensile strength at almost all studied temperatures than its welded joints. In welded samples, by increasing the temperature, the weld metal showed higher deformation resistance than the base material due to the strengthening of alloying elements. While, the strength of S900 HSLA steel which is dependent on the grain boundary strengthening, dropped significantly. S900 HSLA steel and its welded joints experience a rapid decrease in strength when heated to 600 °C and reached 48% and 42% of their original strength, respectively. At 800 °C strain hardening was not observed in the tensile tests. The sudden drop in strength at high temperatures is due to the annihilation of the elastic energy stored in severely deformed grains and the recrystallization process.

Graphical abstract Display Omitted

Highlights • High-temperature tensile behavior of S900 HSLA steel and its welded joints studied. • S900 HSLA steel had higher strength than its welded joints at elevated temperatures. • Formulas for the reduction in mechanical properties of S900 HSLA steel were proposed.