Influence of water environment on wet underwater manual self-propagating high-temperature synthesis welding

Abstract

Manual SHS welding is a kind of quick welding technique for emergency maintenance. In this paper, influence of water environment on the welding quality and performance has been studied. Results showed that water had significant influence on the welding. The visibility for welding was significantly reduced, which increased the difficulty of welding operation. The brightness of weld pool in wet welding were darker than that in land welding and the shape of combusting arc was compressed significantly. The highest temperature of weld pool in underwater welding was obviously lower than that in land welding, and the cooling rate of HAZ was faster. The welding quality was worsen remarkably by water. The weld seam was irregular and discontinuous, and a lot of gas pores and inclusions existed in the weld metal. And the amount of deposited metal was obviously reduced. Microstructure analysis showed that the matrix of weld metal was α-Cu solid solution, with Fe-rich second phase distributing orderly on it, which was same as that of land welding. But water caused many apparent inclusions and pores in the weld metal. The tensile strength of weld joints for underwater welding was obviously lower than that of weld joints for land welding.