Phase II, which began in February 2004, further advanced development of wet welding electrodes and tested the technology on radial surfaces at depths ranging from 50 to 150 meters to simulate the repair of offshore platform steel support/cross members and pipelines. Phase II work was completed in May 2006. See final report located in Reports section below.

Phase III, which began in February 2006, focused on the reliability aspect of manufacturing consumables capable of producing reliable weld joints in structures fabricated from normal grade structural steels as well as the more sophisticated higher strength grades in floating and fixed structures. The applicability of these electrodes were further broadened to overcome limitations found with radial wet welding and weld porosity. Phase III work was completed in November 2007. See final report located in Reports section below.

Phase IV, which began in March 2008, focuses on out-of-position welding (i.e., improve the slag system for faster cooling to remove impurities by driving them to the surface) and other aspects of weld integrity necessary to transition these experimental electrodes for industrial applications. The characteristics of high acicular ferrite, high impact toughness and weldability in vertical positions will be very beneficial on many underwater welding situations.

Porosity quantification, metallographic analyses, micro hardness testing and chemical analyses were conducted on bead-on-plate welds made at 100, 200 and 328 ft. Gravimetric method was used to quantify weld metal porosity. The results exhibited little scatter indicating good repeatability of the process. Literature data shows eight percent porosity for welds deposited in 100 m depth. As expected, porosity increased with increasing depth. Porosity values should decrease when using commercial electrodes or manual welding instead of gravity welding.

With increasing depth, width, and penetration, the heat affected zone (HAZ) width also increased. In contrast, reinforcement and wetting angle decreased. Pores and top bead irregularities were observed which increased with increasing depth. All beads presented limited penetration, which can be improved using direct current electrode negative, DCEN.

The dominant microstructure observed were ferrite with second phase, aligned and non-aligned (FS(A) and FS(NA)), primary ferrite (PF(G) and PF(I)) and martensite (M). Low concentration of acicular ferrite (AF) was observed. Inclusions and micro cracks were also found. As expected, the loss of alloying elements increased with increasing water depth. Adjustment of alloying contents in the final electrodes (to be produced by a commercial electrode manufacturer) will have optimal weld composition and increased acicular ferrite.

The next step to finish all analyses of the first formulation will be mechanical tests, i.e. bend test, Charpy-V notch impact test and tensile tests on V-groove welds.

In March 2009, a representative from the Colorado School of Mines (CSM) presented work to counterparts in Brazil who remain active in the field of underwater wet welding. These counterparts have been performing work on electrode design based on CSM formulations, including waterproofing coatings, flux binding materials, and other methods of extruding electrodes and binders to minimize moisture pickup. Experimental formulations from these Brazilian counterparts show excellent microstructure in welds at depths down to 60 meters. Characterization of these welds is underway.

Discussions with Brazilian counterparts were held regarding international interest in co-hosting the next underwater welding workshop, since the last international workshop was held over two decades ago in 1985. Specifically on the workshop, Brazil indicated that a number of companies and institutions will send people to the workshop and contribute with speakers as well. Plans were made for a kick-off meeting to be held to prepare for the workshop. Funding and organization of this workshop will be made separate from this current study.

Privacy | Disclaimers | Accessibility | Topic Index | FOIA

Last Updated: 03/06/2009, 08:20 AM