Submerged Arc Welding
The SAW (submerged arc welding) process uses a continuously fed consumable electrode (or electrodes) in the form of a wire or strip (for weld overlays) from a coil and a granular flux. The process is similar to GMAW except that the arc is submerged in a granular flux which melts and provides shielding from the atmosphere. Because of the need to hold the flux in place until the molten metal cools, the process is almost always used in the flat position (See Figure 600-18). However, some specialized equipment has been developed for supporting the flux in the horizontal position to make girth seams on large field-erected storage tanks.
SAW is predominantly an automatic welding process with mechanized equipment which controls travel speed. Because SAW is used primarily for welding vessel seams in the flat position, positioning of seams to accommodate welding is required. This requires turning rolls for welding longitudinal and circumferential shell seams and positioners for welding head seams. A wide range of deposition rates can be obtained with the process and even higher productivity can be obtained when more than one electrode is used (e.g., tandem electrodes). Welds are generally of high quality and have good mechanical properties when the proper welding consumables (wire/flux combination) are selected.
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