nitrogen as backing gas

sharjeelfaiz · **Joined:** Mon Oct 15, 2007 6:54 am **Posts:** 128

Hello.

Can we use nitrogen as backing gas for welding of SS materials. Is yes, then do I have to look for a reference paragragh in ASME Sec IX or AWS?

Thank you very much.

Regards,
Sharjeel

raghurambathula · **Joined:** Tue Jan 29, 2008 5:00 pm **Posts:** 103

yes you can use N as backing Gas, as long as supporting PQR justifies per QW408.2

Ballbearing · **Posted:** Fri Aug 01, 2008 12:44 am

raghurambathula,
QW408.2 is applicable to shielding gas and not backing gas.
QW408.5 is the applicable paragraph and that is a non-essential variable.
Regards,
BB

raghurambathula · **Joined:** Tue Jan 29, 2008 5:00 pm **Posts:** 103

yes, it should have been 408.5 instead of 408.2,
thanks for highlighting!

akonrad · **Posted:** Mon Aug 04, 2008 10:30 am

Majority of ferritic (and duplex) stainless steels will have issues when using N2 backing. Refer to steelmakers tech specs.
Austenitic steels may get yellowish, indicating traces of nitridation. You might need to investigate possible consequencies of it.

nitrogen as backing gas

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