Northweldor,
Both CO2 and C25 can easily be used for welding carbon steels. 100% CO2 is cheap but does not give as nice of an arc. Of the two I prefer the C25 due to the cleaner looking arc and less spatter. As shielding gases become higher in argon percentage the penetration profiles begin to change. As more argon is added, the pen profile becomes wider and shallower, however, this is when all parameter variables are held constant in a short circuit transfer. C10 and C15 become used more commonly when guys are looking to move from a short circuit to a spray transfer. Large amounts of CO2 make attaining a spray transfer difficult if not impossible due to the ionization potential of the gas. You can still use short circuit with a C10, but it is more expensive than using a C25 and you are really not gaining much, until you change to a spray.
When welding with a spray tranfer you are able to get deeper penetration than you can by short circuiting even though you are using argon rich gas. To weld in a spray transfer you must have enough amperage (wire feed speed) and voltage. For example, a good starting place to reach this tranfer for an .035 70S-6 wire using C10 would be about 26V and 450 IPM wire speed. This tranfer give good penetration and control with very low spatter, higher travel speeds, and very low cleanup. The down side is spray is not very suitable for sheet metal becase the high amperage will cause burn through, and you are restricted to the flat and horizontal position, because the amps are so high the puddle will not freeze fast enough and will run out of the joint when welding on thicker material. If you looking to weld sheet metal I would recommend using the C25 at about 30CFH in a short circuit tranfer.
Hello Northweldor, as you increase the argon content in a gas mixture you improve the conductivity of the arc. Thus in simple terms the C10 gas operates "hotter" than the C25 does. As you said, you haven't had an opportunity yourself to make this comparison. As an experiment once, I set-up a manifold of shielding gases on a GMAW machine and started out the first weld using 100% CO2, with this gas on the machine I set the voltage and wirespeed to make a reasonable looking bead. Without changing any of the machine settings I switched the gases, using 75/25, 85/15, 90/10, and finally 98/2(I should add, the 2 in this case refers to oxygen), in each instance as the gas was changed to the next higher concentration of argon there was a slight increase in the voltage and amperage that were being put out by the power source.
CO2 does have some unique characteristics as a shielding gas when compared to the mixed gases, at lower volt/amp settings the gas has a cooling effect and can be quite useful for aiding in controlling burn through, at higher volt/amp settings it can actually promote good penetration. The issues with 100% CO2 are usually associated with a considerable amount of spatter, more so from the transfer mode, globular transfer, when the volt/amps are elevated. Hope this helps out a bit, Denny had a good suggestion for you, particularly since he has a considerable amount of experience with the 110v machines. Good luck and regards, aevald
Thanks for the information! I think I am going to stick with a 75/25 mixture for now, but I am going to keep an eye open for a larger tank. One of the local shops quoted me $35 to fill a 20ft tank, and only $45 to fill a large one!
Thanks to all for the detailed information above, and I will print out this thread for our club members who want full details. Also, thanks to Denny for confirming that C- 25 will do the job practically, rather than switching to a 7% CO2 blend (as recommended by the local supplier) at a much higher price. (I think Ed Craig would be also be happy that we are not buying gas blend hype!)
Hey jason280,
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