Shield Gas for Stainless

so, i've been searching around for some info on shield gas for TIG on
stainless. i found a few consistent recommendations, but which one and why?
i do notice that most recommend little or no CO2.
i'm welding 16-20ga. 304 SS using 308L filler via TIG process.
98% Argon / 2% CO2
100% Argon
75% Argon /
25% CO2
96% Argon / 3% CO2 / 1% Hydrogen
98% Argon / 2% Oxygen
90% He /
7.5% Ar / 2.5% CO2
Reply to
Kryptoknight
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for tig you waht 100%argon the othe gasses are for mig welding
Reply to
chopper
With austenitic stainless TIG use can use Ar/Hydrogen.
The gas is sold as such for TIG stainless, certainly here in the UK.
I know as a metallurgist who has worked on hydrogen in welds that austenitic (Cr-Ni) stainless has properties to hydrogen far removed from that of carbon steels by thousands of times and overall, it is very highly immune to hydrogen cracking.
Hydrogen will intensify the arc. More penetrative I think but certainly faster run rate. In reality you must be able to use it all day every day for mild steel, though I've never seen mention of that.
The hydrogen will actually clean the tungsten - as it is a reducing agent.
Any mixture with oxygen or CO2 has to be an absolute no-no for TIG - it would oxidise away the tungsten
Richard Smith
Reply to
Richard Smith
The only gasses used for TIG are Argon, Helium, and, rarely, Hydrogen.
Helium boosts the arc temp and makes for cleaner welds on SS.
CO2 and O2 are forbidden in TIG
Reply to
Ernie Leimkuhler
can you suggest a helium/argon mix for doing 16-20ga. 304-321? i would like to keep gas costs down but at the same time if i'm gonna use helium then i would like a mix that the welds will benefit from.
Reply to
Kryptoknight
We use 100/2% hydrogen everyday for stainless TIG, so much better than 100% argon.
Richard
Reply to
AMW
102%???
Reply to
Pete C.
sorry, 98/2%
98%argon and 2% hydrogen
Richard
Reply to
AMW
Richard - thanks your response - I was thinking folks are going to conclude I'm talking moonshine-talk. Seems unheard-of in N.Am.
So you use the stuff and it is really good?
Richard S.
"AMW" writes:
Reply to
Richard Smith
Yes, it's similar to using helium with aluminum welding. It adds more energy to the weld, makes the stainless puddle appear a bit wetter, (flows better) the arc starting is better, and travel speed can increase. At work we have at every weld station a bottle of argon and a bottle of 98/2 % argon/hydrogen. Using "Y" valves I can select either bottle as my shielding gas, without changing hoses. While you can get mixtures as high as 7% hydrogen, I've found over the years that 2% works good.
Richard
I am writing this from home, that's why my "from" name is different.
Reply to
Art Van Dalay
In article , "Kryptoknight" wrote:
For thin stainless like that I would keep it down to 75% Argon / 25% Helium
Reply to
Ernie Leimkuhler
can 98% argon / 2% hydrogen also be used on aluminum? i ask because i would like to only have 1 tank for now.
anyone experience the hydrogen igniting? i ask because of my recent issue with my torch cup acting like a blow torch for half-a-second right after my arc starts (while using 2% lanthanated tungsten). Ernie's 1st response to me on this is that my argon may have hydrogen in it.....
Reply to
kryptoknight
at the 2% level I've never had a problem, after 10+ years of using it. Hydrogen with aluminum would not be good. I guess helium can be used on stainless, but I haven't tried it.
Richard
Reply to
AMW
Aluminium / aluminum blowholes with hydrogen. I assume, thinking from first principles, that that means no Ar/H2 for Al. ???
On solidification, any hydrogen in the Al melt is rejected out of solution and blowholes the solidifying metal.
About the only metal immune to hydrogen is austenitic stainless steel.
Ar/2%H2 - flammability - surely none at all?
Richard Smith
Reply to
Richard Smith
No flammability at 5%H either. We use this mixture daily on automated circumferential welding of stainless.
Reply to
tomcas

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