Behavior of the Fusion Hole in Tungsten Inert Gas Thin-Plate Welding

Abstract

One-side welding with back formation technique is widely used in pressure vessels and the pressure piping industry. Welders provide high importance to the role of the fusion hole in this type of welding. Therefore, the formation and instability of the fusion hole should be studied to realize the welding automation of the one-side welding with back formation process. A visual sensing system is established to capture the image of the fusion hole, and the behavior of the fusion hole is investigated. Results show that the typical process of the fusion hole includes formation, growth, and macroquasisteady state. The welding parameter scoop to obtain the stable fusion hole is narrow. After deviating from the appropriate parameter scoop, the fusion hole will enter unstable states, thereby resulting in the “fusion hole effect” failure of the welding process. Depending on the change in the shape of the fusion hole, instability types of the fusion hole can be divided into longitudinal, lateral, and gradual shrinking instability. Different instability types correspond to different changing laws of fusion hole morphology. The instability characteristics of the fusion hole can provide effective early warning information before the “fusion hole effect” failure.