Behaviour of high strength steel butt joints exposed to arctic low temperatures

The present study investigated the tensile behaviour of high strength steel (HSS) butt joints exposed to arctic low temperatures. Two HSS grades, namely Q890 and Q960, with thicknesses of 6 mm and 8 mm, were employed. Single-V-groove butt joint specimens were fabricated by means of robotic gas metal arc welding using 1.2 mm-diameter ER100S-G and ER120S-G feedstock wires. The single-V-groove and butt joint tensile specimens were designed according to the Structural Welding Code-Steel AWS D1.1. Metallographic observations and Vickers hardness tests were performed on five series of HSS butt joint. Moreover, a total of 25 butt joint specimens were tested under uniaxial tension in a liquid nitrogen cooling chamber, with temperatures ranging from -75 °C to 25 °C. The stress-strain histories, tensile strengths and failure modes of the HSS butt joints exposed to arctic low temperatures are fully reported. The influence of low temperature exposure, parent steel grade and weld material selection on the tensile behaviour of the HSS butt joints is discussed. Based on the test results, recommendations for weld material matching for Q890 and Q960 HSS butt joints are provided. Additionally, prediction equations for HSS butt joint strengths exposed to arctic low temperatures are proposed using the best subset regression analysis. The findings from this study contribute to a better understanding of the behaviour of HSS butt joints under arctic low temperatures, and can be used to inform design and fabrication practices of HSS structures in cold environments.