Argon back purging
Argon back purging
(OP)
Hi,
Recently I came across a very old WPS for welding alloy steel (ASTM A 335P22 to A 335P22). The WPS recommended use of argon back purge? Is that common to have back purge and what is the advantage of having it while welding. I am aware of back purge in stainless steel and risk of oxide formation due to temp.
Recently I came across a very old WPS for welding alloy steel (ASTM A 335P22 to A 335P22). The WPS recommended use of argon back purge? Is that common to have back purge and what is the advantage of having it while welding. I am aware of back purge in stainless steel and risk of oxide formation due to temp.





RE: Argon back purging
For the lower chromium content (5% or less) Cr-Mo steels an argon back purge is not necessary. I have on occasion seen it used for extra cleanliness requirements but these are rare. The back purge simply protects the weld root from exposure to pick-up of oxygen and nitrogen, while protecting the surrounding base material on the ID side of the weld joint from local oxidation.
RE: Argon back purging
RE: Argon back purging