Gas Metal Arc Welding Process Parameter Optimization to Reduce Porosity Defect in a Longitudinal Seam Welding of Pressure Vessels

Pressure vessels are critical equipment used in industries for storing liquids or gases at a pressure significantly different from ambient conditions. Porosity is one of the major weld defects in pressure vessels that leads to failure during inspection and as well as during its service. Gas Metal Arc Welding (GMAW) process is widely used in industries to fabricate pressure vessels using carbon steel "IS 2062 E250BR" material for storing compressed air. The main objective of this article is to reduce the porosity defect in the longitudinal seam (LS) welding of the pressure vessels. Detailed analysis is carried out to identify the parameters which are influencing the porosity defect. Central Composite Design (CCD) and Response Surface Methodology (RSM) approaches are used to find the optimum value of the weld parameters which produce weld without porosity or any major defects in the pressure vessel. An experimental setup has been established and welding experiments have been conducted under a controlled environment. Experiments were conducted without any external disturbances ensuring clean weld surface and filler wire without any moisture, rust, oil, and the presence of any organic materials. For all the weld specimens, visual and radiography examinations were carried out to identify the severity of porosity. A porosity index is proposed in this study for conducting statistical analysis. Statistical analysis shows current, travel speed, gas flow rate, and torch angle have a linear relationship and stickout distance has a nonlinear relationship with porosity. In square term, stickout distance has a significant influence on porosity defect. In two-way interaction studies, current and gas flow rate, current and torch angle, and travel speed and torch angle have a significant influence on porosity. Confirmatory tests were carried out to validate the optimum weld parameters obtained in this study.