Summary of Wet Underwater Welding

Underwater welding is a kind of professional technology for underwater welding of metal structures. Underwater welding has both water and high pressure effects, so the technology, equipment and quality requirements of underwater welding are different from those of land. At present, there are many underwater welding methods, which can be roughly divided into wet underwater welding, dry underwater welding and local underwater welding.

Wet underwater welding, that is, divers do not take any drainage measures and direct welding method. With this method, the main problems encountered are poor visibility, difficult to control, fast cooling speed and high hydrogen content, which affect the quality of welded joints.

In 1954, the concept of dry underwater welding was first put forward by the United States, that is, to weld a wide range of water, including the welded parts, in a dry gas tank environment. The main problems of this method are as follows: firstly, there must be a large cabin, but its adaptability is poor due to the limitation of the shape and position of underwater welding workpiece. So far, this method is only applicable to the welding of simple structures such as submarine pipelines; secondly, there must be a complete equipment system for maintenance, regulation, monitoring, lighting and safety control, which is expensive. Thirdly, the influence of pressure on welding quality still exists. With the increase of water depth, welding arc is compressed, arc column becomes finer, weld bead and weld width become narrower, weld formation deteriorates and easily causes defects.

Local dry underwater welding: wet underwater welding, simple equipment, easy operation, low cost, but poor welding quality. However, dry underwater welding, although of high quality, is expensive and has poor adaptability, but it is difficult to meet the growing development of marine development. Therefore, people have developed a local dry underwater welding. This welding method is to discharge the local water around the welding site artificially to form a local gas tank area in which the arc burns steadily. Compared with the wet method, the quality of the joint is improved because the interference of water is eliminated in the welded part. Compared with dry process, it does not need such a huge equipment system. So this underwater welding method is the focus and direction of current research. However, this method also has some shortcomings, such as poor flexibility and adaptability, long welding time, smoke thickening, affecting visibility. Because of the frequent location of mobile devices, the quality of weld joints is not guaranteed.