The
ONLY time straight argon is used with GMAW (aka MIG) is for aluminum (or maybe copper or magnesium or titanium, except in 'thicker' pieces where argon-helium blends would be used for additional heat).
Strong statement. But true.
GMAW with straight argon on steel ('plain' or stainless) is not recommended because of the real lack of fusion/penetration you would get and the non-recommended compatability with the wire electrodes/fillers.
GMAW on stainless steel, in short-circuit transfer mode, where you actually want to end up with still-stainless and thus use a compatible filler (such as 308/308L on 304 base material)
and compatible shielding gas such as tri-mix or an argon blend such as 98-2 Ar-O2 or 95-2/95-5 Ar-CO2. If you use shielding gas with a higher CO2 percentage than that, you can (or may, especially if running multiple passes) run into excess carbon pick-up and thus no-longer-stainless weld beads.
murphy, C25 is just fine and recommended for most GMAW on mild steel with solid wire filler/electrodes in short-circuit transfer mode.
As to using a shielding gas with an FCAW wire? Forget about it. FCAW-G (aka 'dual-shield', which is a ESAB 'registered' product line/name for their FCAW-G wires) are certainly fine and have their uses, but the 'little' wire-feed welders such as the OP's Lincoln 135 (120V machine) do
not have the correct amperage-voltage output power in order to run those wires at anywhere near the correct operating parameters. Not to mention the FCAW-G wires all seem to come on the 'bigger' spools and would not even fit in his 'little' welder's wire compartment (which can fit 4 inch and maybe 8 inch diameter spools, but will not fit the 12+ inchers) or the 'bigger' wire diameters such as 0.045 and up (Lincoln is listing some 0.045 dual-shield wires on 15 lb 8 inch spools, but his 'little' machine doesn't have the output power to run that diameter and type of wire anyway, example Lincoln 0.045 Outershield 71Elite at 21+ V and 125+ amps, unless he really-really-really wants to find and pay for some Lincoln Outershield 71M p/n ED026804 in 0.035 on a 15 lb 8 inch spool and run it at ~20V and ~100 amps with C25. But that would be for plain mild steel and not stainless steel anyway.
).
As the the OP's desire for "pretty welds", especially on some stainless, that usually means GTAW aka TIG. A pretty skilled MIG welder can make those 'pretty' welds, but those kinds of welders are usually very-very skilled. As in they are kind of sentient robots, ala ZTFab (check out his MIG welds, just fereaking b-e-a-u-t-i-f-u-l).
Use the right 'tools' for the job. When welding, that includes the machine and the filler and the shielding gas and the operating parameters and the person.
