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Material applications
SAW material applications include carbon steels, low alloy steels, stainless steels, nickel-based alloys, and surfacing applications (wear-facing, buildup, and corrosion-resistant overlay of steels). SAW is frequently used in heavy structural construction. It is also used in the pressure vessel industry, chemical plants, and shipbuilding.
Properly performed Sub-Arc welding should consistently result in mechanical properties that are at least equal to that of the base metal. Ductility and impact resistance should be good, and bead appearance should be uniform.
Variations of the Submerged Arc Welding Process
The submerged arc welding process may be varied in a number of ways to give it more capabilities. These include, but are not limited to, varying the number of wires and power sources, adding iron powder to the flux, and using a strip electrode for surfacing.
Multi-wire systems offer advantages, because the use of more electrodes can improve deposition rates and travel speeds. The utilization of more than one electrode in submerged arc welding may be accomplished with either a single power source or separate power sources for each wire.
The use of multiple power sources with two or more electrodes allows for the utilization of different polarities on the electrodes. Also, with separate power sources for two electrodes, alternating current may be used on one, while direct current is used on the other electrode. Typically, when three wires are used in the tandem position (one electrode is placed in front of the other), alternating current is used. The electrodes are connected to three-phase power systems, which are used for making high-speed longitudinal seams on large pipes and fabricated beams.
Adding iron powder to the flux increases deposition rates of submerged arc welding, but it does not decrease the properties of the weld metal.
The utilization of a strip electrode for surfacing may be done to save money. This particular welding system uses the strip electrode and flux to make a corrosion-resistant overlay on a less expensive base material such as stainless steel. During this procedure, a wide, uniform bead is produced that has minimum penetration. The uniform bead is necessary to provide a smooth overall surface. The strip welding system is often used for overlaying the inside of vessels. The flux that is used in strip surfacing is made specifically for that purpose.
Advantages of Submerged Arc Welding
Some of the advantages of submerged arc welding include:
Strong, sound welds are readily made
Minimal welding fume is emitted
Minimal arc light is emitted
SAW is suitable for both indoor and outdoor works
Less distortion
Deep weld penetration
Minimal edge preparation
High deposition rates are possible
Thick materials may be welded
At least half or more of the flux is recoverable
Disadvantages of Submerged Arc Welding
There are a few limitations with submerged arc welding. One issue is that welding can normally be performed only in the flat position. The use of a granular flux and the fluidity of the molten weld pool mean that welding is limited to positions 1F, 1G, and 2F.
Another disadvantage of SAW is that welding is normally limited to long, straight seams or rotated vessels or pipes. Flux handling systems can be quite bothersome, as well.
References:
Miller Submerged Arc Welding
ESAB Welding and Cutting, U.S.
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