Welding stainless steel tubes and pipes typically requires back purging with argon gas when using traditional processes such as gas tungsten arc welding gtaw and shielded metal arc welding smaw.
Tig welding stainless steel pipe purging.
Crevice corrosion of the pipe.
Tig welding stainless steel is performed by using a non disposable tungsten electrode with a tig welder for striking up the arc.
A back purge removes contaminants and provides backing but it also adds significant time and money.
Solar flux is one flux cored wire is another.
At first you re required to appropriately configure your welder.
Most weld purging is carried out on joints made by the tig or gtaw welding process.
There are six basic steps to purging a tig weld.
Any welded stainless steel pipe application requires shielding the back of the weld as well as the front when tig welding.
There are a couple of ways to weld stainless steel without purging the back of the weld.
Prepare the pipe ends for welding.
Purging the weld is the best way to protect the inside of pipes from oxidation.
Aquasol water soluble paper provides an excellent barrier used to retain noble gases such as argon and helium within the weld zone during tig welding of stainless steel and aluminum pipes.
Solar flux is a powder that is mixed with methanol to form a cream like paste which is then painted onto the inside of the pipe plate.
I take it your talking about tig welded root runs.
When the laser welding process is chosen joints or welds being made on reactive materials will need to be carried out and in the case of electron beam welding this is carried out in a vacuum in which case purging takes place by complete evacuation of all gas.
If you re welding stainless steel pipe with a traditional process like tig or stick it likely requires a back purge with argon gas.
They are able to be placed within close proximity of the weld zone thereby increasing efficiency of the entire welding process.
This process also uses shielding gas against contamination but you can weld thinner metals more efficiently with it.