With the development of modern high-strength steels, the application fields have gradually transferred to low-temperature environments, such as deep sea or Arctic regions. Therefore, weldability has become a new challenge, especially low-temperature toughness. To satisfy the requirement of welding engineering in the low-temperature environment, the composition design of welding wire and optimization of welding parameters usually are regarded as highest-priority considerations. Moreover, for some special weldments, such as hot-bending pipe and heavy elbow, heat treatment will be used after welding, and thus it also will become one of the most crucial steps. Therefore, a series of experiments from the development of welding wire to double-sided submerged-arc welding for pipeline steel, multi-pass welding for offshore engineering steel and post-weld heat treatment for multi-pass welded heavy elbow are completed in the present study. The results indicated that the optimization of alloying elements (Mn/Ni/Mo) in welding wire and welding parameters could ensure the ductile to brittle transition temperature of weld metal lower than •60°C. Moreover, ~130°C interpass temperature is more suitable for multi-pass welding of offshore engineering steel. Although it was easy to form some brittle reheated zones in multi-pass weld metal, it was found that there is an insignificant effect on toughness through conventional tempering — an obvious improvement through the combination of quenching plus intercritical annealing and tempering as formation of ~6 vol.% retained austenite and decomposition of M/A constituents — and it is practically viable in an industrial scale.
2019 STEELSIM Conference Proceedings
Xuelin Wang, Zhiwuan Wang, Zhenjia Xie, S.V. Subramanian, Chengjia Shang