A literature survey was made to review presently available information on underwater welding processes. The fundamentals of underwater welding presented in this report were based on the three-year research program entitled "Fundamental Research on Underwater Welding" (conducted from July, 1971 and June, 1974 at M.I.T. for the National Sea Grant Office). In this report, techniques of improved underwater welding processes recently conducted both in this country and abroad are discussed.
The complete understanding of underwater welding phenomena is relatively limited to some lumped predictions of bubble dynamics, heat transfer mechanisms and the varying welding conditions. It is well recognized that a thicker molten flux must cover the puddle at all times to reduce the cooling effect during the underwater stick-electrode welding process. A heavier slag forming (waterproofed) flux-coated electrode, along with a higher current setting and slow welding speed, are required for underwater stick-electrode welding. A completely dry gas-filled environment was found necessary for better quality underwater welds.
Some observations and explanations of this phenomenon during a microscopic investigation of underwater welds are presented in this report. The rapid quench-induced cracking of underwater welds can be reduced by several means. There are currently two approaches to the improvements of quality in underwater welds. One such approach is the development of an improved (coated) electrode which meets the requirements for welding underwater in wet conditions. The other, is the elimination of the wet conditions around the arc zone via direct shielding. Finally, three potential methods to achieve direct shielding are presented in the last section of the report.
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| Number of Pages : | 43 |
| Published : | 1977 |
