nitrogen purge

[Azphiks]

Nitrogen gas suggested as a purge for welding a stainless nozzle to heat exchanger. So I thought I would use nitrogen in my torch too. Doesn't work with torch at all. I got nervous and switched the purge to argon before I buggered the job. Rumor is if I keep the gap small and the arc doesn't get near the purge, I would have been ok? Can anybody give me the straight goods with regards to using nitrogen as a welding and/or purging gas for stainless welding?

[H80N]

Nitrogen gas suggested as a purge for welding a stainless nozzle to heat exchanger. So I thought I would use nitrogen in my torch too. Doesn't work with torch at all. I got nervous and switched the purge to argon before I buggered the job. Rumor is if I keep the gap small and the arc doesn't get near the purge, I would have been ok? Can anybody give me the straight goods with regards to using nitrogen as a welding and/or purging gas for stainless welding?

Bad Idea as a Torch gas... it does not work.... stick to Argon

Becoming more popular as a SS backpurge...

[elvis]

Much cheaper than argon for purging!!

[pull-do]

Use to use nitrogen as a purge gas, butt the PEI dept. stopped it, said it caused cracking,,,, never used on the torch, it won't work. The shops use to use the nitrogen because of price, but you have to use more to accomplish the same purge as argon, so it works out in the wash to just use argon, IMHO. Plus you can't use out for nickel base alloys, it won't do the trick.

[blazehaze69]

Re: N2...

I don't believe nitrogen is an inert gas...

John

[H80N]

I don't believe nitrogen is an inert gas...

John

It does displace oxygen though...

Here is an AWS article worth reading on the subject

https://app.aws.org/wj/supplement/WJ_1975_01_s12.pdf

Here is a very good overview of backpurging gasses and techniques

http://www.boc-gas.com.au/internet.lg.lg.aus/en/images/BOC%20Purging%20while%20welding%20brochure351_68116.pdf

.

[blazehaze69]

Re: N2...

Very interesting...thanks!

[OscarJr]

If I'm correct, the main issue with using Nitrogen as a purging gas is the possibility of the diatomic Nitrogen molecule (N2) coming in contact with the electric arc, presumably if there is a slight gap in the joint. N2 is not soluble in the molten weld pool, but if it comes in contact with the electric arc it dissociates (separates) into monoatomic nitrogen atoms, which are soluble, and diffuse into the weld pool causing nitrogen embrittlement. That's only from what I've read researching the subject.

[H80N]

If I'm correct, the main issue with using Nitrogen as a purging gas is the possibility of the diatomic Nitrogen molecule (N2) coming in contact with the electric arc, presumably if there is a slight gap in the joint. N2 is not soluble in the molten weld pool, but if it comes in contact with the electric arc it dissociates (separates) into monoatomic nitrogen atoms, which are soluble, and diffuse into the weld pool causing nitrogen embrittlement. That's only from what I've read researching the subject.

Oscar

did you get a chance to read the "White Papers" that I linked...??

[OscarJr]

Not yet, been up-n-down all day today, lol. I'll have a good sit-down tomorrow and read them in their entirety.

[blazehaze69]

Talking about Argon...

I thought I'd put this in for the heck of it...

I bought a tank of Argon from a neighbor. The label was sort of crappy looking, so I thought I'd do a little checking. I ruled out that it was C25 buy bubbling some of the gas into a beaker of distilled water. I checked the pH with a meter my wife had- she's a retired chemist- and the pH remained around 7.0...
I did the same test with a tank of C25, and the pH went down to around 4.5...

[H80N]

I thought I'd put this in for the heck of it...

I bought a tank of Argon from a neighbor. The label was sort of crappy looking, so I thought I'd do a little checking. I ruled out that it was C25 buy bubbling some of the gas into a beaker of distilled water. I checked the pH with a meter my wife had- she's a retired chemist- and the pH remained around 7.0...
I did the same test with a tank of C25, and the pH went down to around 4.5...

Why not try to TIG with it and see if it is OK or if it eats Tungsten....??

[blazehaze69]

Why not try to TIG with it and see if it is OK or if it eats Tungsten....??

Less time consuming and a bit more scientific...

[H80N]

Less time consuming and a bit more scientific...

Maybe simplistic but effective... reading that tungsten could tell you lot

ALSO... what color is the bottle..?? and whose name is on the collar..??

[blazehaze69]

Maybe simplistic but effective... reading that tungsten could tell you lot

ALSO... what color is the bottle..?? and whose name is on the collar..??

The neck ring is blank (customer owned), and the bottle is grey- which sometimes doesn't mean a lot...