GMAW Gas

[Darmik]

Hey fellow welders I have a Question ;
I have been using C-25 For quite some time now and my welding supplier
suggested that I use C-15.I tried it for a while,In the flat pos it worked very well, In the Horiz pos it did okay a little to much under cut on the last pass,
Verti pos way to much under cut and it looks like after welding I pinched the weld together in the middle and it did not flow into the sides very well,
Over head pos Stringers worked best that I found. AnywayI did all positions In about 30min I didn't have a lot of time to get to know this gas.
My question is: did I give this gas a fair try? What gas are you using?
And have you used this gas?

[Dmaxer]

I normally use C-25 for GMAW short circuit welding. I also have a big bottle of Ar that I use for GTAW that I have mixed with the C-25 in a 60/40 proportion to produce what amounts to 90% Ar/10% CO2 at the GMAW gun. That is, if I need 35 cfh of this mix to do a particular spay arc job, I set the Ar at 21 cfh and the C-25 at 14 cfh. With this mix I have done spray arc transfer at higher voltages/amperages on 1/4" or greater stock in the flat or horiz. position. I have read guidelines published by Lincoln for spray arc that say an Ar/CO2 mix with 18% or less of CO2 will permit spray arc, but I have never tried spray arc with that much CO2, so I wouldn't know from experience. The Miller GMAW guide book says 8% to a max of 10% CO2 is preferred for spray arc.

The Miller book also says that a 92% Ar/8 % CO2 mix serves as a dual purpose mix usable for short circuit GMAW on thinner material and for spray arc GMAW on thicker materials.

Hope this helps a bit.

I