Parameter identification and mechanical characterization of stud and wire arc additively manufactured steel bars for the use in construction

Stud and wire arc additive manufacturing (SWAAM) is a novel manufacturing approach that combines wire arc additive manufacturing (WAAM) with drawn-arc stud welding (DASW). The technology was recently introduced to overcome the production rate limitations of the WAAM process when producing metallic large-scale freeform lattice structures. The characteristics of the technology are especially relevant for applications in civil engineering. Lattice structures for lightweight structural elements and reinforcement structures can be additively manufactured with significantly increased production rates compared to the same geometries produced with WAAM only. However, the mechanical properties of structures produced with SWAAM are not yet known. In this work, three process parameters (welding time, current, and immersion distance) of the DASW process within the SWAAM process were varied while producing test specimens. The specimens were tested concerning their tensile strength, and the fracture surfaces were analyzed in terms of the fracture behavior and their pore area fraction. A stable parameter window consisting of six parameter combinations was identified. The results showed that choosing the correct immersion distance is particularly important when producing SWAAM samples. In addition, low pore area fractions in the welding zone positively impacted the ultimate tensile strength. A pore area fraction of 7.5 % was identified as a limit to avoid fractures in the welding zone (WZ). Up to a pore area fraction in the WZ of 25 %, the specimens showed ultimate tensile strength (UTS) values above 500 MPa, and the required standardized mechanical properties for reinforcement steel were achieved with the SWAAM specimens, validating the suitability of this technology for construction applications.