I use lincoln superarc l56 for all of my mild steel welding along with 75/25 (Ar/CO2) and this works great for GMAW-Short Circuit transfer mode. If I were to switch to 85/15 (Ar/CO2) to perform Spray Arc transfer mode, could I still use the 85/15 (Ar/CO2) for GMAW-Short Circuit transfer mode and how would the welds look compared to the results I get from the 75/25 (Ar/CO2)?
Additionaly, if 85/15 will not accomodate both transfer modes, is there a gas blend that will?
Thanks
MarkA
Mark
It should short circuit just fine.
I think you could start out with exactly the same parameters you were short circuiting with the 75/25 and if the sound is a bit soft and ploppy than reduce by 1/2 volt incriments until you get the same performance and profiles.
In the unlikely case your wire seemed to be stubbing and you could feel the wire pushing back on the gun than just increase voltage by 1/2 volt incriments until good short circuiting occurs.
I really don't think your going to notice much. Especially if your running 0.035 wire.
The idea with higher Argon blends with SC is not that they can't be used, its that they are more expensive, and unnecessary. You will find with higher Argon a little smoother arc, generally less spatter, generally fewer silicon deposits, yet a more narrow fusion pattern (this is especially problematic for sidewalls in grooves). And fusion is already problematic with SC. Still, given the required skill it can be done and is done in Europe quite often where the higher Argon blends are more popular. Especially 80/20. The Japanese favor 100% CO2 for short circuit, but only because Argon is prohibitively expensive there.
aws d1.5 (95) had verbage to the effect that gmaw with ar 80% or less is considered sc (4.14.4). i see that has been removed in the 2002 code.
I'm not familiar with D1.5, but the removal of that statement would problably be best since its wrong.
In short yes you can still short circuit with 85/15mix. 75/25 will run a lot better in short arc but if your looking to spray and use short arc thats would be the max you would want to use. (85/15) Now don't get me wrong it's not going to spray as good as a 95/5 or a 98/2, but 85/15 should get you pretty close to spray arc just find. Whats the application? If were talking aerospace or something of that nature it would be best not to go the cheap route.
To create spray transfer the shielding gas must be at least 80% Argon for steel. 80-90% Argon permits both spray and short circuit transfers (SCMT). Increasing voltage above 24-5 (how much will be determined by the % Argon) will bring the arc into a spray. Gas Flow rates will be 1 1/2-2 times that for SCMT, wire feed speeds will be 1 1/2-2 times SCMT, the wire stick out will be 1 1/2-2 times SCMT (3/4-1" vs 1/4-3/8"), the contact tube will be recessed 1/8-1/4" behind the copper nozzle for spray/flush-1/8" in front of the brass nozzle for SCMT. And note - nozzle type will be copper for spray and brass for SCMT/the guns are rated at 100% duty cycle with carbon dioxide and the argon blends reduce this by up to 50%. The copper nozzle's diameter must be larger for spray, 5/8-3/4" vs 3/8-1/2". Increasing the filter lens shade may be wise. Push gun angles are preferred over drag angles.
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