Effects of CO2 on weld metal chemistry

[meltedEng]

Hello,

Does anyone have a textbook, papers, references, or direct knowledge on the following?

Looking to find the chemistry effects, main concern is carbon content, in GMAW welds of austentic stainless steels from various gases, Ar (no effect or reducing), Ar-CO2 (Effects at 1%, 2% ... ), Ar-O2 (1-2%) vs original carbon contents (0.005 to 0.04).

Thanks

 

I have no references at hand, but I have faced the question before. I am guessing that sensitization and IGA concerns are behind your question, but Austenitic weld deposits are more tolerant of carbon than base metals in that respect.

On steels with very low carbon (any L grade SS), CO2 in the shielding gas tends to increase deposit CO2. The welding process is a chemical reaction that drives toward equilibrium, with gases in the shield gas having activity that is a function of temperature and concentration (Argon and Helium being inert of course).

At high base metal carbon content, low activity in the gas ([C] in chemistry lingo) tends to lower C in the deposit. The traditional gas for GMAW welding of austenitic SS has been Ar-2%O2, but pulsed MIG has opened up possibilities for new gas mixes. Silicon content in the wire is a factor, especially in GMAW where it enhances wetting.

I suggest you reach out to welding technical support experts at one of the gas companies such as Praxair, who will offer solutions tailored to your application.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[meltedEng]

Ironic,

I appreciate your reply, and I like your guess (you are on the right train of thought).

I agree with your comments. I should have been more clear on my initial post: I am looking for a correlation, table, or data, maybe presented similar to how the WRC-92 chart is done that correlates initial C content of austentic alloys to the shielding gas composition with final C content. Or maybe specific ranges empirically determined etc.

You have proposed a great lead, I will contact our Praxair technical contact, they may have this data available.