Aluminum With Mig Help

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Hi guys, first post here, been lurking for a while though, have really enjoyed learning from a lot of you.I was given my first aluminum welding project today, which so far as been a disaster.  It's a 12" pipe, 14guage wall, needed it cut @ 25 degrees and then welded to form a 50 degree angle.I've got a Millermatic 252 with a Spoolmatic 30A, running .030 4043The welder says to set it at 19.7/460About all I can do is burn holes in the pipe at that setting, and trying much lower settings didn't seem to help a whole lot, not enough to make a decent weld.If I turned it down to around 16/350, I could get a weld on the inside of the 50 degree angle, but on the outside or the sides, still blew through it like crazy, especially if there was any kind of gap.Any help/advice would be greatly appreciated.
Reply:Turn the heat up and get some 3/64 wire. Sounds odd but you have to get into a spray form transfer and just motor on!You can run less wire speed that way and the arc wont be as forceful at the start. Get it set on some flat pieces and go from there. Thats my 2 sense at least. Good luck.
Reply:When welding relatively thin aluminum with the 30A, you need to move the bead along fairly quickly with a relatively hot setting.  Don't pause in any one spot.  I make rapid C's and keep going.  Obviously your best bet would be Tig, but the 30A on a MM252 will do the job once you get the weld settings and your motion in synch.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:Is this a rain cap or something non-structural?  If it is, hot and fast vert down will do it.My name's not Jim....
Reply:I agree with the previous posts. AL MIG with no pulse is hot and fast AKA spray and pray.
Reply:It's part of a suction for an irrigation pivot, so it's not really structural, but needs to not leak or it will suck air.
Reply:Thanks for the replies, much appreciated.Do you have any suggestions for settings to start from, or do you basically agree with the 19.7/460?I'll give it another shot in the morning.
Reply:Honestly  as a first Alu welding project a 14g pipe is a hell of a learning curve just try buttoning it up with spot welds almost a manual pulse pull trigger quik whip release wait a sec repeat and if your have issues with a hole try a PC of stainless or even a PC of steel as a backer as for setting I'd try 22volts at 6 on the wire speed with 40cfh of argon good luck
Reply:I would get at least 035 wire but 3/64 is best. I also like 5356 for mig if possible. its less fluid and runs through the gun easier. I would have that at about 24-26 volts. Large range but its so hit or miss with each machine. The goal is a nice smooth hisss with no popping sounds. Also on thin material believe or not i would travel up. If the joint is tight. Also always push the puddle. Its hard to stay ahead if you pull it and leaves a thick black smoke. Have fun!
Reply:Fit up is very important. Thin AL doesn't allow for gaps, it will blow right through as the edges burn out.Miller Dynasty 200DXMiller 252 Miller 250xMiller Syncrowave 250Miller AEAD200 LegendMiller 375 Xtreme plasmaLincoln WeldPak 100Victor O/A
Reply:id just spot it in.  make sure to hold long enough that it penetrates and over lap each spot good so it doesnt leak. sure work fine for something none structural
Reply:I got it welded today, thanks for the help.I still didn't weld it with anything close to the settings you guys are suggesting, did get 3/64 5356 wire though.I tried quite a bit to do it like you said, but i couldn't even pull the trigger without just instantly burning through, couldn't even spot it in at those settings.Got me wondering if you're messing with me?  Haha
Reply:Ha def not messing with you.  What you are trying is a technically difficult weld even if everything is perfect. Considering the fact it was a new process for you its not hard to belive you had problems. I have seen some pretty seasoned welders get all banged up and out of sorts with thin aluminum mig. It is possible though. I have done quite a bit in my time. Takes allot of practice though. Its hard to wrap your head around the fact that you need such high heat(voltage) on such thin material. Good old ac tig will make your life allot easier if you encounter anymore situations like this. Its allot more forgiving. Not always an option though considering the expense of an inverter or even an old transformer unit and water cooler ect.Nick
Reply:Hell a Miller Diversion would have been perfect for welding 14ga aluminum $1800 or so for a new one if you plan on doing a bunch of light aluminum a smaller tig machine would do it. Don't expect to be doing much more than 1/8" with it though.
Reply:you never stated what gas you were using,was it was 100% argon?
Reply:Yes, 100% argon.I was just asked to do another one, so I guess I'll get some more practice!I don't plan on doing much thin aluminum, most should be at least 1/8, probably more like 3/16 and 1/4.  And even then, most of what I do is steel, probably don't have enough aluminum to justify a tig, yet anyhow.
Reply:Crazy question but a big irrigation pipe? Is it located outside where there may be some wind?
Reply:Yes, it's outside, and we get our fair share of wind.  It's pretty much on the ground though.
Reply:Maybe I misunderstood that question, it will be located outside, I had it in my shop to weld it.
Reply:When you want to weld thin stuff scrap material to practice on is a must and clean clean clean even if it looks clean you need to shine it up and wipe it off with at least a wet rag before you weld it. Don't scar up the surface with a course grit paper and don't use steel brushes or sand paper that is dirty or has been used for steel. This thin stuff has to be right to get even close to a nice weld with a spool gun. The spot welding that was talked about does work nice and can look appealing once you get the hang of it and a rhythm going on your overlaps. Back stitching is also necessary on the thin stuff. Just saying.....Fireman BillHH 210 MVPMM 211 Spoolmate 100Lotas LTP5000D PlasmaOxy/Accet (Victor)Wards AC/DC buzz box30 ton old hyd pressA few brand name toolsA bunch of cheap toolsA wife to worry me and4 dogs to supervise me