Purge Gas GTAW penetration question
Purge Gas GTAW penetration question
(OP)
We had a lot of difficulty with our final tie-in welds with concave root and some cracking with Inco 117 filler on 304H and a needle purge on a project.
We are attempting to weld up some test pieces of 800H with 117 (Needle purge) in our shop and discovered that this too resulted in significant concavity without backing gas for the hot pass.
Our second attempt was with a full purge (Argon) and even with a hotter hot pass we were successful.
My question is how would maintaining a purge during the hot pass positively affect the root vs. no purge during the hot pass.
We are attempting to weld up some test pieces of 800H with 117 (Needle purge) in our shop and discovered that this too resulted in significant concavity without backing gas for the hot pass.
Our second attempt was with a full purge (Argon) and even with a hotter hot pass we were successful.
My question is how would maintaining a purge during the hot pass positively affect the root vs. no purge during the hot pass.





RE: Purge Gas GTAW penetration question
RE: Purge Gas GTAW penetration question
I have been in situations where it is not possible to maintain a purge during the hot pass. In these cases you need to turn down the amps of the second pass so that the root pass is not in a molten (boiling) state during the second pass.
Always maintain an interior purge during hot pass if at all posible.
Robert
RE: Purge Gas GTAW penetration question