Effects of Heat Input and Backing Gas on Bead Geometry and Weld Heat Tint in Sanitary Tube Welding

Heat input always plays a crucial role in enhancing penetration depth within the heat-affected zone (HAZ) of the orbital TIG welding process. The heat tint, in addition, caused by heat input, is a decisive factor for the quality of sanitary tube welds, which AWS D18.2 strictly regulates. Therefore, controlling heat input to achieve complete penetration while maintaining an acceptable heat tint level is considered essential in sanitary tube welding. For this reason, this study conducted 27 experimental welds with variations in the parameters of the Orbital TIG Welding process to determine the optimal welding parameters for sanitary tubes with an outer diameter of Ø38.1 mm and a thickness of 1.65 mm. Taguchi analysis identified the optimal parameter combination to achieve full penetration as a welding current of 100 A, an arc length of 1.5 mm, and a welding speed of 5 mm/s. In addition, the use of internal backing gas and arc time significantly improved the heat tint level of the welds produced under the proposed parameter set.