Submerged Arc Welding (SAW) is so called bacause the tip of the welding wire, the arc, and the weld joint are covered by a layer of granular flux. The purpose of the flux is to act as a shield against spatter, fumes, and sparks, clean impurities from the weld metal, help prevent contamination and oxidisation, and shape the welding bead. In some cases, flux alters the chemical properties of the weld by adding alloy elements to the metal.
The process of SAW uses the heat of the arc to melt the surface of the metal and the end of the electrode to become the deposited weld metal. Flux covers the weld area and generates gases and slag to provide a 'glass-like' shield during the process.
Advantages of SAW:
- High travel speed
- Deep penetration
- Safe to use - no visible arc or spatter
- Weld quality is high and consistent
- Fully automated - Beam-mounted, portable tractor or semi-automatic systems for heavy fabrication environments.
- High productivity and deposition rate - It is possible to weld very large joint areas with fewer passes.
- Easy set up.
- SAW can be carried out both manually and by mechanised techniques. Mechanised welding is used in the majority of applications.
'The machine does most of the work. The user just has to adjust the parameters when necessary. The new equipment is fairly simple for the operators to run."
Mike Flagg, SAW manager for the Lincoln Electric Co.
Flux comes in powder or granual form and can be mixed to create a paste, depending on the application it is used for. As with anything these days, it is important to choose the right kind of flux for the job otherwise there is a risk to the overall join quality. There are different fluxes for different metals and applications, such as but not limited to, aluminium and aluminium based alloys, steel, bronze, iron and ferous metals.
Flux Handling: Unopened packages should be stored in dry conditions. Once opened, packages should be used immediately or kept in a humidity controlled store for re-use and dried according to manufacturers guidelines. Slag or dust particles may change the composition of flux and could cause blockages to the feed system
SAW is slightly different to other welding processes, in that it doesn't produce high levels of spatter or fumes - depending on what is being welded. - and normal workplace extraction should be sufficient.
In terms of what the welder should wear, normal gear, such as a head shield and leather apron is often not necessary, although it is important to follow workplace procedures in place.
Other PPE such as goggles, heavy gloves and protective shoes are required for related operations such as chipping or grinding.
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