Understanding and overcoming of abnormity at start and end of the weld bead in additive manufacturing with GMAW

Abstract

Weld bead geometry at start and end of the bead is often abnormal compared with the middle region, which will greatly affect the forming in gas metal arc welding (GMAW) additive manufacturing. The study’s aim is to investigate the causes and the optimization strategy of the weld bead abnormity at the unstable region. The weld pool dynamics, convection, and the extension process were analyzed through a three-dimensional transient fluid model and the finite element analysis of thermal behavior. The results showed that the abnormal bead geometry can be attributed to the backward fluid flow and the metal swelling in the weld pool, and the length of the initial bulky region is positively correlated with the inclined shape at the end, as well as the length of the weld pool. Some strategies to control the bead abnormity through adjusting the welding parameters, the crater filling options, and the path planning patterns were proposed. These methods contributed to the continuous and smooth deposition surface and laid the foundation of GMAW-based additive manufacturing process.