Underwater Welding : Shipbuilding Materials
The underwater welding diver should be familiar with the different types of steel used in shipbuilding in order to select the appropriate welding electrodes. Today shipbuilders have a wide range of steels which are used in the construction of ship’s hulls and superstructures. Quite often, ship hulls are comprised of more than one type of steel. A ship may have stronger steel at the keel, garboard and sheer strakes and at the turn of the bilge where the stresses are higher. In these cases, electrodes of higher strength steel are applicable. Perhaps the simplest approach to these materials is by strength, although this is not the only criteria for selection. Often times, accurate information is not readily available when needed. A quick, field-expedient method to determine the type of electrodes to use is as follows:
a. Cut a small sample of the material to be welded and make a Tee fillet weld specimen
b. Wet weld the specimen and break it with a sledgehammer. If it breaks easily after being welded with mild steel electrodes, it is more than likely that the steel is of a high carbon content and should be welded with austenitic electrodes. On the other hand, a specimen that bends a great deal before breaking indicates low carbon content and may be welded with mild steel electrodes.
NOTE Very high strength steels, like HY-80, are not recommended for wet welding because of cracking problems stemming from the intense heat produced by the welding process followed by rapid cooling of the weld metal by the ambient water.
For high strength steels, a stainless steel electrode gives better results.