Characterization of the weld zone of Grade AH36 steel ship plate joined at the real marine conditions through underwater welding

摘要

In this study, Grade AH36 steel ship plate was joined at both the atmospheric and real underwater conditions at ascending different depths through shielded metal arc welding process. The isolated E6013 rutile electrode was used in welding process. The welded specimens firstly subjected to visual inspection and this was followed by radiographic test. Bending and impact toughness tests were also carried out in order to determine the mechanical properties of the welded joints. Microstructural examines were performed to observe the structural transformation and hardness test was also conducted on the weld zones. Non-destructive test results showed that the specimens joined underwater had weld defect such as slag remains on the weld surface and between the pass, gas porosities, grooves and the lack of penetration. According to the bending test results, when the difference of water depth increased, the tests resulted in adversely at some angles due to defects like remains, gas porosities etc. on the weld metal. With respect to impact toughness tests, the specimens welded at atmospheric conditions presented better toughness than the others. The maximum hardness value was measured from the weld metal and this was followed by the heat affected zone (HAZ) and base metal sequentially. Microstructure evolutions showed that structures of the weld metals were dendritic, rolled structure of the base metal in the HAZ was destroyed and partial grains growth was seen in this section.