Investigation on the weldability of cold-formed ultra-high strength steels S700MC and S1100

Abstract

Hollow sections and cold-formed steels have a key role in modern structures and machinery. In addition, to benefit from full potentials of cold-formed steels, it is usually required to weld them to other parts of the structure. However, data provided by relative standards, such as Eurocode 3, do not cover newly developed high strength grades of steels, including Ultra-high strength steels. Thus, further study is necessary to complete available data in standards. Regarding this matter, having a good weldability for cold-formed ultra-high strength steels seems to be vital for development for contemporary steel structures. Thus, newly developed ultra-high strength steels S700MC and S1100 were selected to be investigated in this study. To do so, bended base metals with different levels of cold-forming were welded to straight (virgin) steel plates. Next, welded joints were investigated via microstructural analysis, hardness measurement, tensile test, and Charpy impact test to assess the weldability of cold-formed base metals. Results show that final joints had acceptable characteristics, and cold-formed base metals showed good weldability. However, this conclusion was true if the pre-strain values recommended by Eurocode 3 and manufacturer were satisfied. Beyond that criteria, some premature failures occurred in the cold-formed materials after welding.