Building strategy effect on mechanical properties of high strength low alloy steel in wire + arc additive manufacturing

Abstract

Wire arc additive manufacturing (WAAM), which is literally based on continuously fed material deposition type of welding processes such as metal inert gas (MIG), tungsten inert gas (TIG), and plasma welding, is a variant of additive manufacturing technologies. WAAM steps forward with its high deposition rate and low equipment cost as compared to the powder feed and laser/electron beam heated processes among various additive manufacturing processes. In this work, sample parts made of low-alloy high-strength steel (ER120SG) were additively manufactured via the WAAM method using robotic cold metal transfer technology (CMT). The process parameters and building strategies were investigated and correlated with the geometrical, metallurgical, and mechanical properties of the produced wall geometries. The results obtained from the thin-wall sample parts have shown that with increasing heat input, mechanical properties decrease, since higher heat accumulation and lower cooling rates increase the grain size. The tensile test results have shown that casting steel (G24Mn6+QT2) mechanical properties, which require 500 MPa yield strength, can be compared to the as-built WAAM process, which has 640 MPa yield strength. Tensile strength was fulfilled for S690Q, and yield strength is very close to the reference value.