Having trouble with MIG/exhaust pipe

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I'm new to welding and I've had my Lincoln 3200HD (25-135A rated) for a couple weeks now.  I've been running beads and such on old scraps.  It's setup with Innershield flux core .035.  I've got some 3" exhaust tubing scrap cut from a larger piece I plan to weld up this weekend so I'm practicing with it, hoping to find the right settings.  No, my machine does not have infinite V adjustment.  I started on 'B' and instantly burned through the scraps - two pieces butted-up together.  Dropped down to 'A' and it works mostly but I'm still poking 1/8-1/4" holes in it if I don't move quick enough.  If I move too quickly I leave the pool and get dunes as the wire bounces off the surface.I prepped the tubing by brushing back any surface coating with a wire wheel on a drill and it's clamped to a 24"x24" 18ga surface with the Lincoln's clamp on the tubing itself.  The clamp has new nuts and washers and still works well when practicing on other surfaces.I've run some pretty good beginner beads on flat, thick surfaces where burning through was not a concern.What am I doing wrong?  Should I be weaving back-and-forth?  Try .030 wire?  Longer stick out?
Reply:FCAW on thin tubing is tough to do.Practice.Or try some 0.030 FCAW wire (Innershield NR-211MP just like you have now, except in the 0.030 size).Or move to GMAW and try 0.023/0.025 wire or 0.030 wire and C25 gas.  And practice some more.The manual says voltage B and wire speed 1.5 or 2, for thin work with 0.035 Innershield NR-211MP wire.Per the manual, thin work with 0.025 L-56 wire and C25 gas would be voltage A and wire speed 2-2.5 until your workpiece thickness gets up to 18 gauge.Practice.  It takes time and practice to be able to weld thin stuff.  Practice on some 1/8 inch thick steel for a while so that you can see the puddle and what is happening as the arc melts the steel and the wire fills in the puddle and so forth.  With that machine, 1/8 inch steel is thick enough to be able to see  whats happening without instantly burning right through.  Usually.  Although it can burn right through 1/8 inch steel with the 0.035 Innershield NR-2211MP wire, it has the oomph to do that if you turn it up some.  The best laid schemes ... Gang oft agley ...
Reply:I have a dinky Lincoln weldpak 100hd that I have done many exhaust repairs with I use .30 flux core wire like moonrise suggests. As you already discovered A is the setting to be on, and i usually dial wire speed down a lot to get more "control"adding a bit of weave/side angle helps keep it from melting back from the seam as well. Butt welds are the hardest on tubing with a welder like this
Reply:Gentlemen, thank you for taking the time to reply.  Hearing that this is a difficult feat from more experienced welders is a mixed blessing.Were I to expand the pipe and snugly fit one inside the other, then weld at the overlap, would this improve my chances?  Would it then still benefit me to change to .030 wire?
Reply:Originally Posted by viper522Gentlemen, thank you for taking the time to reply.  Hearing that this is a difficult feat from more experienced welders is a mixed blessing.Were I to expand the pipe and snugly fit one inside the other, then weld at the overlap, would this improve my chances?  Would it then still benefit me to change to .030 wire?
Reply:What are common uses for .035 FCAW?  I understand the previous owner worked with entry gates and the like, probably thick iron bar?  I'd like to know what I can use it for in the future since I'm going to shelve it in favor of .030.Thanks
Reply:.030 and .035 self shielding flux core wires are light duty structural wires.  They can be used for repair and/or building of things like gates, grills, handrails, etc.  Pretty much good for anything that isn't going to have a large amount of stress.
Reply:The .035 NR211MP (multiple pass) structural Lincoln wire is way too much.Use a smaller diameter wire.The exhaust tubing is probably .049 or .065 thickness.AWS certified welding inspectorAWS certified welder
Reply:I do a LOT of exhaust, but I use bare wire with C/25.  I also always start at the top and run down to the bottom.  Weave back and forth to weld the two pieces together.  A lap joint is far easier than a butt.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:A lot of OEM exhaust on vehicles are a Stainless mixture to help prevent corrosion.  It's a real B**** to weld.  If you are using a mild steel wire, gonna be hard to get a good weld.  After market exhaust stuff can be successfully welded with O/A, MIG, TIG, ARC.Get a spool of SS wire, should work ok.
Reply:There are certain metal core wires that will work with exhausts, but they are probably very expensive.
Reply:Don't have an O/A torch?
Reply:When I first started hobby welding, which is what I do, i had many burn thru problems on thin stuff. Eventually I moved up to MIG with C25. All I can say is cut out the "starbucks" for a few weeks or something and get a bottle of C25 and a roll of solid .025 wire. The gas makes everything easier and prettier and cleaner. The thin wire I have found is perfect for hobby uses as it is a little slower down the line and I have more control on smaller items. It's not what I would use to fab a utility trailer (.030 or .035 for that) but it sure is easy to control cuz its laying down material slower.My 2 cents and keep in mind I'm no expert by any stretch. Lincoln PowerMig 180cVictor O/ABandaids and aspirinI don't know what I don't know!?
Reply:For me the setting chart on the door of the 3200HD is almost dead nuts on.How thick is the wall of your exhuast tube? As others have said you may have to go with gas and solid wire on the real thin stuff.
Reply:I did some of the initial work yesterday.  I wanted to try it with what I have first, .035 flux, before making a bunch of changes.  There were a couple problem areas where I had to grind down and weld it again, but overall it looks decent.  It's all covered by high heat paint and stuffed under a car so 'pretty' isn't my highest priority.I have settled with setting A,2-1/4 and weaving back and forth.  Instead of doing butt welds, I made a sleeve out of scrap pipe that goes around the exhaust pipe and butts against the larger pipe, creating an overlap.  Doubles the welding, but what the heck I need the practice anyway.  The off-the-shelf pipe expanded just wasn't able to make the smaller pipe large enough for a tight fit.