Comparison of Solidification Behavior Between Underwater Wet Welding and Dry Welding

The solidification substructure, both mode and size, has influence on the mechanical properties of weld joints. Controlling the solidification substructure by obtaining finer grains will generally result in enhancement of the weld joint quality and properties. Thus, it is essential to understand how welding parameters including voltage, current and weld travel speed as well as the welding environment (air and water) affect the solidification substructure. This work presents the effects of welding parameters on columnar grain morphology for both wet and dry welds. Also it compares the solidification rate and columnar grain size (width and length) between the dry welds and wet welds. For fair comparison, the welding parameters of both dry welds and wet welds were maintained similar. The solidification rate of wet welds is faster than that for the dry welds. A maximum difference of 22% was observed at half distance from the fusion line to the weld centerline. For wet welds, the observations revealed that the average columnar grain width and length of wet welds decrease with increasing electrode angle and decreasing welding travel speed. On the other hand, the columnar grain width decreased with increasing welding current. Also, as the welding current increased the average columnar grain length increases. Dry welds differed from wet welds in that the columnar grain average length decreased as the welding current increases. Moreover, the wet weld columnar grains are finer than those found in the dry welds at low welding current, namely 110A and 120A, whereas the wet weld columnar grains are comparable or coarser at high welding current, e.g.130 A and 140A. Statistical analysis of the columnar grain aspect ratio data set using Student’s-t test resulted in low t-value, 0.329 for low current welds, while high t-value, 7.775, was obtained for the welds made at high welding current. Results revealed that the columnar grain morphology in wet welds and dry welds are statistically different at low welding current 110A while columnar grains in dry and wet welds are similar at high welding current 140A.