Anybody with much experience with MIG on pipe.

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Currently at work we have a Stainless Steel Pipe job.  The pipe is 4" Schd 40.  Usually when I weld it I'm set at about 22V, and 200IPM, knife edge, 5/32 gap (On initial fit up,  which usually sucks into about 1/8 after tacks.)  When the fit up is ideal and it sucks into the 1/8,  I feather out the tacks and the pipe basically welds itself.  But,  say when the gap sucks into less then 1/8,  I have a hard time getting the root in at those settings.  So instead of taking the time to grind it out and make it ideal,  what do I want to do to give me more penetration to rip through that smaller gap.  Is it as simple as adding abit more voltage and turning down the wirespeed a bit?  I've been messing around a bit, and haven't found anything I'm really happy with.  That's why I'm here looking for somebody who could help me out.  Thx.
Reply:It seems most people will root with stick or TIG and cap with MIG.  MIG doesn't give the control of temperature other methods do to allow you to root over a wide range of conditions without having to constantly mess with settings.But, if you want to increase penetration, I would say your best bet is to increase your wire diameter.
Reply:in position or rolling it out? .035 lsi wire? trimix i'm 99% sure of with those settings...though they lead me to believe you are using .045 wire. Rolling it out with an 1/8th in gap I would run my root at 19.6v 220ipm with .035lsi wire and trimix slightly on the downhand side. If it were me. granted its going to depend a lot on the machine, manufacturer of the wire, etc and so on. stainless is so friggin picky. Might try turning down your volts and wire speed and just moving a little slower. The heat will build up in the work piece a bit more and help with the penetration further into the weld. Provided you dont overheat the ss of course.Last edited by i4sillypwr; 12-15-2010 at 02:04 AM.
Reply:Off topic: What are you doing to keep from sugaring the inside?  If it is purge, you can turn down the purge pressure to get a little more penetration.  If it is a product like Solar Flux, turn up the heat, but be careful once you get to the flatter section as it will make your puddle larger and the potential for it to fall through is increased./Assuming that you're not rolling it out.