Humbled by a MIG

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Well, I can weld pretty darn good with my AC/DC Sickmate. With nice dry rods and clean material, my welds are actually strong and very presentable.So...I get a brand new exhaust system for my musclecar, requiring fabrication from the headers to the midpipe......and of course welding. So I buy a MIG.Hobart 140 Handler, 75/25 argon/co2. 030 wire...the whole she-bang.My buddy and I spend half the day cutting and grinding to fab the 2, compound S bends required, tack 'em and everything fits perfect.Now sand every joint clean, wipe with acetone and get ready to weld.The exhaust is 18 ga. "aluminized" steel, so I set the machine just like Hobart says and holy crap!  Burn through, ugly welds, not getting the right sound. I tried slowing the feed and lowering the voltage.......everything. I'm hoping the issue is the "aluminzed" steel.Anyhow I got one side welded. Not pretty at all, but appears strong. I gave up for the day.Can anyone give me a few pointers for welding today's aluminized exhaust pipe?The stuff I'm working with is mandrel bent, heavy wall, very high end pipe. I thought with good stick skills this MIG thing would be easy. Man was I wrong!
Reply:Is this the first time ever? Have you done any test coupons? What wire are you using, most new out of the box units are shipped with flux core wire?
Reply:.024 or .025 wire is easier on the thin stuff.
Reply:My hobart handler 140 didnt come with flux wire but it was wired for it. It did come with the Mig regulator open the side panel it will tell you where to put the two wires
Reply:Yeah, if the machine is setup for fluxcore it'll make a mess with solid wire and gas. Been there done that.
Reply:Set up properly for solid core wire. Using .030 ER70S-6 with 20 cu ft gas. Might pick up a roll of .024 before I start tomorrow.Yeah. My first time with a MIG. Right now it seems waaay harder than stick welding. Maybe I'm just biased. Before I totally despise this thing, I'm gonna play around a bit with some 1/8th plate I have laying around. I have the feeling real steel might be a bit different than the aluminum/steel hybrid exhaust pipes.
Reply:I dont think its the metal..Ive done tons of exhaust work with my .030 fluxcore, low heat, slow speed and allowing metal too cool works for me.I did learn that running solid wire through my flux used liner makes a difference. A now have spare liners for solid, and aluminum...Lincoln Power MIG 210 MP ( boat anchor )Lincoln Weld-Pac 100 HDHobart IronMan 230Cutmaster 42Jackson NexGenSumner Ultra ClampsDWM120
Reply:Originally Posted by ctmikeSet up properly for solid core wire. Using .030 ER70S-6 with 20 cu ft gas. Might pick up a roll of .024 before I start tomorrow.Yeah. My first time with a MIG. Right now it seems waaay harder than stick welding. Maybe I'm just biased. Before I totally despise this thing, I'm gonna play around a bit with some 1/8th plate I have laying around. I have the feeling real steel might be a bit different than the aluminum/steel hybrid exhaust pipes.
Reply:Maybe a good idea to pick up some mig gun dip or spray.
Reply:Watch out for th fumes when welding aluminized exhaust pipe. I heard it can be nasty.Lincoln ProMig140
Reply:Pick up tips for the .024 wire.
Reply:What is the aluminum content???When I MIG weld aluminum I use 100% argon, not a mix.Scottwelders360.comNew guy.
Reply:Are you sure the polarity is set right?  Also, are you sure you're actually geting 12-20 cfm of gas to the tip?  Sometimes the gas part of the lead isn't seated right and the C25 is going somewhere else.  Too high a gas flow can also cause problems.  A loose connection where the ground lead meets the clamp can also cause problems.(All of this is advice from a beginner, so take it accordingly,)Jack OlsenMy garage website
Reply:I would not call 18 ga high end pipe. It might be what the auto parts store had but 16 ga is the standard pipe at any good muffler shop that custom bends pipe. It might not sound like much but when it comes to exhaust pipe it's a big deal. You'll find that 16 ga is much easier to weld.Tough as nails and damn near as smart
Reply:My mistake. I meant 16 ga. pipe. Mandrel bent. 800 bucks is high end, in my book. Especially if it ain't stainless. These days if you want a quality system for an early Mopar, you're gonna pay.Anyhow, we finished it all up today, running less power and slower wire speed, I kinda got the hang of it. Welds are not real pretty, but they are strong and secure.I WAS right about the exhaust pipe Vs. real steel. Got done so early today, I cleaned up a few pieces of 1/8 plate and ran some butt joints and a few fillets. WOW! What a difference real steel makes. Those welds look like a chassis shop did 'em. Real nice penetration....no spatter. I am now a MIG fan. I don't think I'll even fire up the stick machine, unless I have something heavy to work with.Thanks for all the help, guys!
Reply:Run your welds downhill. You haven't posted settings, but I would say to set the heat at C, or 3 out of 4, and set the speed at about 4-5. Faster than you might expect. The heat set lower with .030 wire will not get hot enough to keep the puddle well. It does do better with .023/.024. Downhill welds will get less penetration, less holes.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:FYI, next time if you are running a new/different machine and/or a new wire/filler and/or some new/different work pieces, always PRACTICE on some scrap first and not the actual item you want to weld.  New machine and brand new to GMAW?  Try some practice doing a lap joint on some clean 1/8 inch steel.  Lap joint so you can see the arc melt the edge and so you have a double thickness of metal at the joint to minimize the 'instant blow through' factor.  Practice and adjust things and see how they all interact and make things change for the weld.After that, -then- practice on some tube.  Tube ain't so easy to do right or well, and thin tube (well, thin -anything-   ) can be easy to blow a hole right through.Practice, practice, and practice some more.  After you feel confident in the general usage and then on the usage on the specific material (size and configuration) done on scrap, -than- you go and weld up your actual item.Doing it that way cuts down on the 'ooops' factors.Also note that GMAW in short-circuit mode is -notorious- for making welds that look 'OK', but are actually just cold-lapped aka inadequate penetration aka inadequate fusion aka just sitting on top of the base material and not actually welded well.  Sheetmetal thickness is usually easier and better with 0.023/0.025 solid wire and the C25 gas compared to 0.030 wire.  The best laid schemes ... Gang oft agley ...