## 3 Results and Discussion
### Macro-Section Analysis and Weld Morphology  
To understand the bead shape obtained at different settings of current and EN ratio, macro-sections of welds were analyzed. Figure 6 shows the macro-sections of welds obtained at varying settings of current and EN ratio. The dotted line in macro-section represent fusion boundary (FB). Different bead shape parameters such as penetration depth (\(P\)), bead width (\(W\)), reinforcement height (\(R\)) were measured and the resultant findings were presented in Figures 7-9, respectively. At lower values of currents, the penetration depth decreased with the increased in EN ratio. The penetration depth is less at 50% EN ratio as compared to 0% and 30% at lower value of currents. It is observed that at higher values of currents, the increase in EN ratio resulted in an increase in penetration depth. At Ia of 225 A and 250 A, an increase in EN ratio resulted in an increase in penetration depth. However, it is more noticeable at a 50% EN ratio. The maximum penetration depth was achieved at a 50% EN ratio. The increase in the penetration depth at higher values of currents and EN ratio was a result of the intense plasma jets generated along the weld pool axis. The intense plasma jets generated in the weld pool axis resulted in the higher temperatures at the center, which resulted in finger-like penetration. The above results are in reasonable agreement with earlier results published by [PERSON] and [PERSON] (2015) on BOP welding. Increasing the EN ratio at high currents results in deep penetration, which is very useful for thick plate welding. According to Figure 8, at an EN ratio of 30% and 50%, bead width increased with an increase in current from 150 A to 225 A, and it decreased at a current of 250 A. The reduction of bead width at higher Ia of 250 A is due to the molten metal deep penetration in the weld joint axis. As a result, a low value of bead width was obtained. The maximum bead width was obtained at an Ia of 225 A and a 50% EN ratio. At an EN ratio of 0%, bead width increased with an increase in Ia up to 200 A, and then it decreased with the increase in Ia. Figure 9 shows the comparison of reinforcement height at different EN ratio and Ia. It was found that reinforcement height increased with an increase in Ia from 150 A to 225 A and it decreased at an Ia of 250 A. Maximum reinforcement height was obtained at Ia of 225 A and 0% EN ratio. Figure 6: Macro-sections of welded joints at different Ia and EN ratio. The macrographs of welded joints at Ia of 250 A with different EN ratios are presented in Figure 10. The surface appearance of the weld bead revealed spatter free weld joints at all EN ratios. Figure 8: Comparison of bead width (\(W\)) at different EN ratio and Ia. Figure 7: Comparison of penetration depth (\(P\)) at different EN ratio and Ia. Figure 9: Comparison of reinforcement height (\(R\)) at different EN ratio and Ia. Weld face showed reasonable weld quality in all cases. However, at Ia of 250 A and a 0% EN ratio, no penetration of molten metal in the root side was observed. However, at a 30% EN ratio, reasonable root side penetration was observed. At a 50% EN ratio, root side showed the desired penetration throughout the weld line. However, it is noticed that the excess of deposited molten metal on the top of the plate requires higher welding speed and optimal joint gap. Macro-section analysis shows that the sound weld joints can be obtained in single pass welding of a 5-mm thick steel plate using higher value of currents and EN ratio. Furthermore, good gap bridging capability is obtained during pulsed AC-GMAW of thick steel plates. Among many factors, joint gap bridging ability of the deposited molten metal is one of the principal factors affected by joint gap tolerance. The appropriate joint gap results in optimal gap filling. With a small joint gap, the deposition of molten filler metal caused a build-up of metal on top of the weld, leaving the weld with excess weld metal profile. As a result, the required joint lacks completely filled grooves.