American Welding Society Forum
Can you please advise if purge gas is required or applicable for FCAW welding. We have a general requirement stated in our document that the root weld of stainless steel pipes/tubes must be protected from the atmosphere by an inert gas shield
during welding and subsequent cooling. Purge-gas protection for the weldment has to be used. Our supplier states this in not applicable or needed for FCAW. Why would this be? Thank you
There's some miscommunication / misunderstanding going on with your supplier.
FCAW electrodes comes in two basic types, one that requires shielding gas (through the weld gun to protect the arc) and another that does not.
This has nothing to do with internal purge gas on SS pipe.
If you can do an open root with FCAW or SMAW on Stainless, then you could possibly have a fully shielded root pass on the back side. This is possible but not easy. I have qualified with open root SMAW on stainless before for window welds and its very fitup/amperage/technique critical.
For Stainless FCAW, I am sure the possibility exists to do the same thing but that does NOT change the requirements of your document. If your supplier has some open root Stainless FCAW skills, I suggest asking for a demo!
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