Effect of automated MIG welding process parameters on ASTM A 106 Grade B pipe weldments used in high-temperature applications

This paper presents the investigation on welding of ASTM A 106 Grade B pipes to access the quality of weldments for mechanical and metallurgical characteristics by varying the influencing factors such as voltage, wire feed rate of the filler material, and gas flow rate of CO2. The experiment was conducted using an automated MIG welding setup that has the capacity to weld the pipes with diameter ranging from 20 to 90mm. Further the welded samples are subjected to various tests to identify weld defects, weld bead geometry, microstructure, hardness, tensile strength, and fractography. The output responses such as reinforcement form factor, penetration shape factor, and tensile strength of the material are analyzed using Taguchi method and optimized results were reported and validated. The direct and interaction plots drawn between input parameters and output responses serves as a good indicator for achieving the quality weldments by the appropriate selection of process parameters. Fractography of the weldments signifies the type of failure is brittle in nature and the fractured surfaces consists of microvoids, double dimple sizes, shear lips, plastic flow, and cleavage facets.