Fatigue properties of welded Q420 high strength steel at room and low temperatures

Engineering structures are erected in all kinds of terrain and climate, and structural deformation and vibration may appear in anytime, such as deflection, shrinkage-expansion and vibration response. Fatigue failure of steel structure is a long-term behavior and difficult to estimate, especially in low temperatures. To study the fatigue behavior of Q420B steel weld joints under low temperatures, this paper conducted a series of experiments. Firstly, Charpy V-notch impact tests and strength tests of Q420B steel under normal and low temperatures were performed, and this type of steel can meet the requirements of Chinese and American standards. Secondly, the test specimens, temperature control system and loading method were designed, after which the fatigue tests of Q420B steel weld joints were carried out under different stress amplitudes (0.5 ftw, 0.7 ftw and 0.9 ftw) and different temperatures (25 °C, 0 °C, −15 °C and −30 °C, i.e. 298 K, 273 K, 258 K and 243 K), respectively. The fatigue fracture occurred at all above stress amplitudes and testing temperatures, and the fatigue life obviously increased with the decrease of temperature. Therefore, it can be concluded that the low temperature can improve the fatigue performance of welded Q420B steel in some degree. Lastly, the S-N curves of Q420B steel weld joints under different temperatures were provided and compared with the theoretical values of the current specifications.