Weld morphology and mechanical performance of marine structural steel welded underwater in a real marine environment

Abstract

Grade AH36 ship steel plate, frequently used in offshore applications, was joined underwater by shielded metal arc welding (SMAW) using two different types of electrodes (E6013 and E7014). The ship steel plate was also joined under atmospheric conditions in order to compare both joints in terms of mechanical and metallurgical properties. The E6013 rutile electrode was isolated by wrapping before use, and the underwater welding process was carried out at a depth of 8 m under the sea. The joints were first subjected to visual inspection and then liquid penetrant, ultrasonic, and radiographic tests were performed. In order to determine the mechanical properties of the joints, tensile, bending, and impact toughness tests were also carried out. In addition to the microhardness test on the weld zones, microstructural examination was also performed on the joints. As a result of the nondestructive tests, weld defects like slag remaining between the passes, gas porosities, burn-through, and lack of penetration were seen on the joints welded underwater with the two different electrodes. The study determined that these defects had significantly influenced the mechanical properties and width of the weld zone of the joints.