Question regarding GMAW pipe under 4":

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Long time reader, first time poster. Any help would be very much appreciated.I seem to be having an issue welding pipe under 4" in the 6G position with MIG. We run downhill, one root pass cleaned with grinding wheel, and one cap pass. Using an old Miller (not sure exact model. Has voltage crank and separate feed mech.), with 100% C02, ER70S-6 .035 wire, CFH at roughly 25-30. Usually my voltage will dial in anywhere from 18-19 volts, and between 245-300 IPM. Pipe has to be gapped at an 1/8 inch, and the landings vary depending on what you're handed. They range from 1/8" to a 1/16". Usually under 4", the pipe will have a 1/16" land. The pipe is all sch. 40, but ranges from 1" 1/4, all the way up to the occasional 18". Everything exceeding the 4" diameter will run very smooth at the settings I have described. Good root fusion without undercut, and the cap has no lap or fallout.On the pipe under 4", I run 2 tacks roughly 1/2" in size. Have tried moving tacks from 6-12, to 3-9.. so on and so forth. Have changed my settings numerous times in both directions. The tacks go in smooth on the v-block at 16.5+ and 225 IPM; but, when welding, the piece seems to get too hot and I have a lot of blowouts/keyholes. Not so much whiskers on the inside, but way too many starts and stops to create a smooth looking root. For the cap, it will run smooth until the 8-4 range on the lower quadrant of the pipe. Even on lower settings, you can tell the puddle is too hot and will out run you and booger up at 6 o' clock. I try and keep a slight drag to dead nuts gun angle. And I keep roughly a 3/8 arc length.So, would anybody be able to pin point what might be happening on the smaller diameter pipe? If more info is needed, please let me know. Again, any help is much appreciated.Fizz.
Reply:To add:I have used the same settings (18-19 volts, 245-300 IPM) on 2" pipe during 1G rollout welds and the run flawlessly.I'm really frustrated as to whether this concerns my technique or the settings I'm using.
Reply:Small thin pipe heats up real fast. You either have to turn down or stop and air cool the pipe, maybe both. Blow an air hose on it. Why are you trying to weld in 6G, assuming you are already certified?Are you the only one having trouble? Tell your boss to switch to TIG for that small pipe.
Reply:We have to run cert tests for different customers depending on what they want done. And we re-certify with the company every 6 months.I've tried turning down the voltage but can't seem to find a happy medium between good fusion and blowouts. Possibly too slow of travel speed?The company only runs GMAW because it's basically a speed shop. You can never get anything done fast enough. Lol.Even on the caps at around 16the volts, it will be very grey with an almost fluxcore appearance and will occasionaly eat thru all the pipe at 6the o' clock.
Reply:Try running a root pass, then a split bead cap.  Faster travel will help keep the pipe from overheating.  In short arc you can turn the WFS down some as well as the voltage.  try 17-18 volts and 180 to 220 IPM wire feed speed.  See if this helps, might make too much spatter with 100% CO2.  Is switching to 75/25 an option?  The CO2 is adding penetration, and that doesn't do you any favors on the bottom of the joint.  The 2 bead cap and lower settings will cut down on the heat input and give you better odds of not blowing through the root.  It'll also freeze faster and lay flat on the overhead section of the cap.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Split bead is no go. Single pass only. And we can only use 100%card CO2 for API 1104, or that's what I'm told.I'll try playing with the WFS some more.Thanks!
Reply:I always have a terrible time running 100% co2 with hardwire, the bead is always dull and it just doesn't do well on pipe.. At work when we put the bead in we run our machines at 16v and about 160 on the wirespeed, and that is 2" to 24" pipe.
Reply:Justin,You're definitely correct on the dull aspect. Almost as if the weld has a thin slag coating. I will try those settings out tomorrow as I don't think I've dropped wire that low yet. We have 2 other pipe welders at work. One is struggling in uniformity on the cap, and the other has already passed using similar settings. And he has a distinct freeze line pattern on his cap with no sag or greyness.I would ask them for advice, but the language barrier, well... yeah... http://www.mig-welding.co.uk/gas/co2...hield-thin.jpgMy cap looks very similar to the lower weld in the photo (which is strange), even with torch manipulation. Which is another reason that makes me believe I'm going to slow and letting the puddle build to much since I can't see any distinctive pattern.
Reply:OK.  Your weld procedure is only for 100% CO2.  For the record, there's nothing in API1104 that states you must use 100% CO2.  but if your bosses don't want to qualify another weld procedure with 75/25, I can understand that.  Same for the split bead cap.  OK.The only other thing to do is adjust wire feed speed, voltage, and inductance.  Not sure what power supply you're using, but you might gain some more control by fine tuning the inductance, if possible.  If you have inductance control on the power supply, try welding on some scrap while another guy makes small changes.  You should be able to smooth out the transfer and improve puddle control.I'm out of ideas at this point.  More practice may be your only solution... Originally Posted by fizzySplit bead is no go. Single pass only. And we can only use 100%card CO2 for API 1104, or that's what I'm told.I'll try playing with the WFS some more.Thanks!
Reply:Settings used on these pieces were 18.8 volts, and 280 IPM with 25+ CFH 100% CO2.Cap on 1G mechanized rollout. 2 inch sch 40.Root on 1G mechanized rollout. 2 inch sch 40.6 o clock position on 1" 1/4 6G.12 o clock position on 1" 1/4 6G.Same results on 2 inch 6G. It just seems that the puddle gets too large and uncontrollable, and it's very hard to find settings to produce same quality coverage and penetration with CO2.Oy.. Time to go postal.
Reply:A dab,The only welders with inductance features are the ones being used by the welders with seniority. I'm using a Millermatic 3something or other with a voltage crank and a 22A wire feeder box. My other machine that broke had a high and low inductance setting lead lug to switch over too, and I did not have as hard of a time when I was using it. But there's an internal short and the machine is down.I guess I'll just have to keep running different settings until I get it. I was hoping it would be a more obvious solution I wasn't getting. I appreciate the help.