Backing gas for P1 to P8

Date 04-03-2007 15:18 Edited 04-03-2007 15:22

Is a backing gas required if I am welding P1 to P8 with GTAW ER309? Even though this is a dissimilar weld, I am assuming that the root pass will still have some sugaring without the backing gas?
Thank you very much!

By js55

Date 04-03-2007 15:31

You will definately need a backing gas with this weldment to eliminate extreme oxidation.

By jon20013 (*****)

Date 04-03-2007 15:51

I agree with js55. While there are GTAW rods that have a flux which supposedly eliminates the need for purge gas there has been much discussion on that matter with (in my opinion) no true consensus. Purging should be the route you take. Argon is usually the gas of choice.

By troilite (*)

Date 04-03-2007 15:52

Thank you very much js55 and Jon for your helpful advice!