Best way to MIG weld thin 16 gauge mild steel tube with CO2 only shielding gas?

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Hi everyoneI've been reading this great site for a few weeks and now decided to post.What's the best way to MIG weld 16 gauge 1" or 2" square and rectangular tubes using only CO2 for cost reasons?It's for a semi-spaceframe so stresses should be somewhat limited to tension/compression.What electrode type/ size to use?Is negative electrode better?What Voltage/Amp settings to use?Thanks guys
Reply:Co2 runs hot, so you're gonna fight that.If it's solid wire (you're not dual shielding) you don't have much choice RE DCRP, that's kind of the way you have to goSettings.. what machine? 110 V home store Lincoln, 12,000 dollar multi process pipepro, whaddaya got?I've done a lifetime's worth of 16 GA squaretube using C25 and a Millermatic 135 (ancient equivalent to the current autoset 140) and it's a bit of a bitch. Weaving sometimes across a gap, straight and easy fillet stringer when fitup is perfect, you gotta kinda roll with it.What's your fitup like, chopsaw cuts or standalone bandsaw?The more info you give, the more help you're gonna get.I wouldn't do this with straight CO2, it'll piss you off more that the extra 30 bucks a bottle, but then these days I've learned to factor frustration and rage into a job cost analysis, some younger guys aren't there yet.If you fight long enough, you will win. The problem is it costs too damned much.- Lee Cheng
Reply:I use CO2 exclusively with my MM252. It does run a bit hotter than C25 but you can turn the machine down a bit to compensate. A good trick is to keep a jar of welding gel handy and dip the tip in the jar now and then when it's hot. It virtually eliminates spatter and the tip stays nice and clean. I like CO2 for the extra penetration is gives as well as the price. I pay $25 out the door of the local LWS for a 20# cylinder exchange. C25 is closer to $60. I spend the difference on adult beverages.  Miller Millermatic 252Miller Syncrowave 200Liincoln AC-DC 225Victor O-A Set
Reply:We used the MM35 for years on C02 for doing wrought iron work using 035 wireBacked my CATMA over your CARMA oops clusmy me  What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite  Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:Been there done that, no big deal. Dial the machine in and have at it. I run 100% CO2 for all my steel MIG and never have an issue.
Reply:Originally Posted by TozziWeldingBeen there done that, no big deal. Dial the machine in and have at it. I run 100% CO2 for all my steel MIG and never have an issue.