Gas composition and GMAW

[bpeirson]

How does extra CO2 affect the GMAW process?

Specifically switching to 75%-25% Ar & CO2 from 92%-8% Ar & CO2.

 

[Duwe6]

"Colder" gas; much higher probability of Lack-of-Fusion when running Short-Circuiting mode. However, 75/25 has been the historic choice for GMAW-SS. And historically, LoF has been a major problem. Personally, I would go to 80/20 or 85/15.

 

[gtaw]

If you are welding carbon steel or high strength low alloy steels for a structural application in accordance with D1.1, you should be using spray transfer. The higher percentage of Ar is going to promote spray transfer when compared to the gas with less Ar.

Generally, the minimum percentage of Ar to ensure a stay spray transfer is 80%. Reducing the Ar content can result in inconsistent transfer mode, i.e., the process alternates between short circuiting and spray transfer. The encourage spray transfer with the low Ar content, the arc voltage has to be increased.

you can spray with 75% Ar, but it tends to be somewhat unstable. I usually limit the CO2 to 12% or less when spray transfer is required. The 92% Ar *5 CO2 gets my vote every time.

Best regards - Al