Nitrogen purge for open-root GTAW 310 SS

By another1 Date 02-23-2016 00:03

I realize that nitrogen purge is common enough for closed-gap pipe welding, and that there are potential concerns with nitrogen in the shielding gas where it is exposed to the higher temperatures and arc-side of the puddle. What about open gap GTAW where the purge and shielding gas are more commingled? Does anyone have experience or references to confirm this is a non-issue or otherwise. I found a paper on closed gap welding indicating non-issue, but wondering about open-gap/open-root.

By Lawrence (*****)

Date 02-23-2016 12:43

Welcome to the forum Another!

My experience has been that open gap with nitrogen is problematic, via destabilizing the arc. But that is just the experience of a welder using nitrogen on a closed gap and encountering the odd poor fit-up.

The link below is from Huntington Fusion, They are in the purging business and have published many articles and white papers on various purging strategies. Michael Fletcher is their senior engineer and I bet he would give you some guidance.

general@cob-industries.com

Phone: Toll Free 1-800-431-1311

By another1 Date 02-23-2016 15:49

Thanks Lawrence for the kind welcome and for sharing your first-hand knowledge. Your experience supports my concern.

By Stringer (***)

Date 02-24-2016 01:16

Nitrogen is cheaper, of course, but it is a reactive gas. Since any problem at all with purity in my argon causes problems with color (and resulting corrosion) I can't imagine that Nitrogen is good for anything except fuel tank purging. But I admit I have not tried it or researched it in any way.

By js55

Date 02-24-2016 16:43

I've seen nitrogen used in GTAW shielding for duplex SS's. Though it is uncommon and is used in very small volume. Perhaps 1% to 2%. For the reason mentioned in Lawrence's post. It destabilizes the arc.
The idea fro duplex is to assist in restoring N content to the weld metal that is lost in welding.
outside of this I do not ever remember seeing it used for shielding. It is common in purges however.