Review of Opportunities and Challenges for Additive Manufacturing of Steels in the Construction Industry

Additive manufacturing (AM), or 3-D printing, encompasses a range of technologies that "print" material layer by layer to create the final part. Though there is significant interest in the AM of concrete in the construction sector, opportunities for the AM of steel still need to be explored. This review focuses on the AM of low-alloy steels, stainless steels, duplex stainless steels (DSSs), precipitation-hardened (PH) stainless steels, and tool steels, highlighting the challenges and opportunities of employing AM technology for construction applications. Fusion-based AM technologies, such as wire arc additive manufacturing (WAAM), laser powder bed fusion (LPBF), and laser-directed energy deposition (LDED), are the core technologies that have been tested in the industry so far. WAAM has seen the most exploration for construction applications because of its higher deposition rate, larger build volume, and lower cost than other AM technologies. The mechanical performance of low-alloy steel, stainless steel, and tool steel shows increased tensile strengths after AM processing compared with wrought counterparts. Although AM is not economical for geometrically simple metal components or geometries, there is potential for AM to fabricate unique structural connections or joints, optimized load-bearing columns, and even entire bridges, as highlighted in this paper. AM's digital nature (i.e., using computer-aided design (CAD) to create G-code paths for printing) can increase structural efficiency if coupled with topology optimization methods and high-strength alloys. Currently, however, general applications of AM in the industry are limited because of barriers with structural codes and standards not incorporating AM parts and AM technology barriers (i.e., limited build volumes).