Submerged Arc Welding (SAW)

Research "narrow gap welding" and you will find articles similar to:

http://www.thefabricator.com/ArcWelding/ArcWelding_Article.cfm?ID=552

have you considered a diametric orbital unit?

no mate...

i intend to know what process would produce lesser defects in narrow groove.

SAW or GMAW?

There is practically no limit on the diameter that may be welded with the SAW process. Fixturing is the element that determines the best use of this process. If you can turn the pipe quickly enough you will be able to weld .188" wall pipe very nicely.

The narrow root opening is one of the reasons to use SAW. Again the speed of the fixture may be reduced to allow for deeper penetration. Also by increasing the wire speed or reducing the voltage the penetration may be increased.

The main reason we use SAW at our plant is that there is almost no possibility for Hydrogen to be entrapped in the weld. Secondly, we are able to utilize the various fluxes to enhance the chemical and mechanical properties.

The GMAW process may be used but the narrow root opening is not readily penetrated with the "short circuiting" or "spray" mode of transfer. The "Pulsed Arc" mode of transfer will work. With .030" wire the thin wall pipe may be successfully welded. Most pipefitters and boilermakers prefer to use the GTAW process for the root pass and SMAW or GMAW for the balance.

thank you profemeritus,

for boiler components, what process will prove fruitful in terms of lesser defects?

SAW or GMAW?

GMAW is prone to cause lack of fusion in narrow groove welding.

But on the other hand, it gives good impact properties as compared to SAW because of finer beads.

It depends on which boiler components you are referring to. If you are doing steam drums, etc. with rather thick walls, I would prefer the submerged arc process. Impact properties will be good with submerged arc if you choose the proper flux and wire. There are exemptions in the code for certain types of welds and materials. There are methods of preheat and post-weld heat treatments to aid the impact properties.

The GMAW process works well on thinner parts such as boiler casings but on thicker parts more passes are required and thus more possibility for non-fusion between the passes. Sometimes the rapid heat input inherent with GMAW will cause problems with the impact values.

We prefer to utilize the GTAW process for the root pass when practical. This process also minimizes the possibility for Hydrogen entrapment. It also gives the welder near complete control of the arc and the weld puddle.