Mig welding stainless overhead..need help!!

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I'm working at a job welding on 304 stainless with 308/.035 wire. Gas is 90% helium, 7.5 and 2.5 co2 and argon mix. What the heck do I have to do to lay just one nice bead overhaed? I tried higher heat, lower heat, faster and slowed wire feeds. I just can't seem to run a consistant bead overhead! It seems like the gas is just evaporating the wire as it feeds out and just keeps blocking the nozzle.  I do eventually get it filled in but alot of grinding and rewelding. Help me please! All thoughts will be greatly appreciated.
Reply:Are you able to run flat position welds with that setup?I would make sure that the settings are correct for running in other positions first, that way you know that everything is working how it should and you just need to adjust a few small parameters to compensate for being overhead.Try tuning the welder for flat position and bump the wire speed up a hair to compensate for being overhead.- Paulhttp://all-a-cart.comWelding Cart Kits and accessories
Reply:Overhead is fun.     Once you "get it" you will have it for ever.  I find a little less voltage or faster wire speed seems to help the wire from burning before it gets to the plate.   Adjustable inductance helps too.  As Welderwmn sez, use the same settings as verticle up.  Start just running stringer beads.  I find if I move ahead a little, then wait for the puddle to catch up, then move again it works quite well.  Good luck.  Practice, Practice.....DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Sometimes the motion you use makes all the difference. Is one side of the seam thicker than the other? Is one side higher than the other? For me it helps to blast the thicker side of a seam with more heat. And also it helps to use a motion that cooks the wire slowly from the higher side of a seam to the lower side and then blink back up to the high side. You can avoid a big pile of metal drooping from the low end that way.
Reply:It is running quite well on flat welds and vertical down is pretty good also. There is alot of carbon when finished welding though. What is with that? I know I did a stainless job before and the welds were much nicer. These welds have to be almost perfect also, Otherwise I've been told they will leak and that can't happen or they will have to be reworked until the leak is stopped. It is a paint system chemical spray booth that has tanks with thinners stainless panels that sit across the tanks. Thanks for the info I'll try other wire speeds and voltage adjustments. Although I already did!!
Reply:My guess is that the 90% Helium mix may just be too hot/fluid for overhead, and your arc length/voltage is too high.  If this is a critical job it may pay to try a cooler gas mix like Ar/2-5% CO2.http://files.aws.org/wj/2006/02/wj20...j200602-46.pdfHelium requires a higher arc voltage than Argon, thus dumping more power to the weld, amps x volts = watts.And to make it even worse, Helium conducts heat many times greater than Argon, thus transfering the higher wattage to the metal."It seems like the gas is just evaporating the wire as it feeds out and just keeps blocking the nozzle." (mackman1962)Sure sounds like Excessive voltage!  Sounds like you are trying to spray transfer in the overhead position.  As mentioned by DavidR, I'd agree that lower voltage (shorter arc length) should help."There is alot of carbon when finished welding though." (mackman1962)The "carbon" or "soot" like deposit along the toes of the finished weld is primarily Manganese Oxide formed from Manganese in the stainless steel reacting in the arc.  First time I saw this was in 100% Helium TIG welding of stainless, and I had the stuff analysed in a mass spectrometer.  For some reason (hotter arc maybe), you get more of this with Helium shielding gas as compared to Argon.