MIG Welding Aluminum?

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Greetings, I have been doing MIG of steel for a while and I do ok with that. I am not a professional or anything, just a hobbyist but I have never had a weld break on me though I would like to be able to do nicer looking welds. Anyway, I have been considering building a Gooseneck travel trailer on top of an aluminum flat bed gooseneck trailer. The basic idea is to buy the base trailer pre-built and then build the shell for the camper on top of that base. The reason I am not welding the trailer up myself is that the critical welds for the rolling chassis are best left to the professionals for safety reasons. Anyway so when I acquire the trailer, I intend to use 2" square aluminum tubing to fabricate the living quarters shell. This will require welding a lot of aluminum tubing connections. So there is where my questions come in. Assuming I acquire a spool gun, what are the essential differences in welding aluminum versus steel with the MIG process. I don't have a TIG rig so that is out of the question unless someone wants to give me a syncrowave 200 for my birthday.  What techniques are important for mig welding aluminum other than using a spool gun and 100% argon? Is push preferred or pull? Do I need to run hotter than for steel? Do I need to heat treat the joints afterwards and can I do that with my Oxy Acetylene torch? Oh other questions: When it comes to fabricating would you think I should weld all four sides of the junction or would two be sufficient? Finally, can I grind down aluminum mig welds smooth like steel to make sure I can put the aluminum siding flush with the tube? Any information you can provide would be helpful. Thanks.Last edited by yorzaxt; 10-21-2010 at 12:46 AM.
Reply:Originally Posted by yorzaxtAssuming I acquire a spool gun, what are the essential differences in welding aluminum versus steel with the MIG process. I don't have a TIG rig so that is out of the question unless someone wants to give me a syncrowave 200 for my birthday.  What techniques are important for mig welding aluminum other than using a spool gun and 100% argon? Is push preferred or pull? Do I need to run hotter than for steel? Do I need to heat treat the joints afterwards and can I do that with my Oxy Acetylene torch?Oh other questions: When it comes to fabricating would you think I should weld all four sides of the junction or would two be sufficient? Finally, can I grind down aluminum mig welds smooth like steel to make sure I can put the aluminum siding flush with the tube?
Reply:I replied to your same post over on Miller.  I will also concur with DSW that you should prepare your butt joints with a bevel and be sure to do a full penetration weld if you will be grinding them flat for sheet fitment over the joint.  I also concur about welding all 4 sides of each joint.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:The Lord has declared, "This is my work and my glory--to bring to pass the immortality and eternal life of man"  Moses 1:39Link: My name is John, and I am a member of The Church of Jesus Christ of Latter-Day Saints.-- ColdCreekWorks.com --
Reply:Yeah I am aware of the cost of the tubing but when you put together an RV with 30k worth of equipment and appliances a couple grand for the tubing is small potatoes. And the reality is that its only about 30% more than steel of the same size via my suppliers.
Reply:In this economy a used RV Trailer already done built would be a much better route.Damn near giving them away on the used market.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Originally Posted by Broccoli1In this economy a used RV Trailer already done built would be a much better route.Damn near giving them away on the used market.
Reply:http://losangeles.craigslist.org/ant...013366405.htmlhttp://losangeles.craigslist.org/sfv...012053989.htmlhttp://losangeles.craigslist.org/sfv...011436168.htmlFabricating something of yer own is rewarding- build on brutha Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:I have a Northtraile 28BRS that I have had 2 years now. I could tell you things about those trailers that would make you balk at buying any of them. I dont NEED another trailer, I just WANT one.  I want a plush one with hydronic heating, built for boondocking with a gooseneck hitch for maximum articulation.
Reply:I own one too and like anything coming off the production line they do have their problems Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Wow, Ed, those big 3-axle fifth toy haulers are priced maybe 1/4-1/3 of what they probly cost new only a few short years ago!  I remember when my friends were buying those big new toy haulers in the mid-2000's for $50-80K, new diesel pickups for $40-50K, buggies for $20-50K, a fleet of new bikes for $4-8K each, most of it on credit card, second mortgages, etc.  I guess they lost their jobs and their 3500-sqft houses and sellin off their kingdoms now.  How times have changed...  I'm glad I stuck with my 20 year old paid-cash-for trucks and toys and kept my living costs in check through the good times, to weather it through the bad times.  MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:I can identify with the dream of building your own rv.  I've often thought about building a custom gooseneck race/toyhauler trailer with living quarters and all sorts of cool design ideas.  Wouldn't be cost effective, even in a very strong rv market, but it sure would be cool.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Used $600,000 USDEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Originally Posted by Broccoli1Used $600,000 USD
Reply:Hey Ed, how about a nice surplus unimog and radio box instead. Attached Images.No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Yeah that is really not my style. I dont need to travel in Iraq. I want a posh RV capable of four season camping.
Reply:Just a comment on that spray Al MIG video from Weldingtipsandtricks.com, I'm no expert on spray Al, but the arc length (work to wire tip) he is running in the video apears at least 2 times what I would expect to be ideal.  I know a long arc with pulsed spray on steel causes problems with bead irregularity and poor wetting which can result in missed fusion along one toe or the other.  Any spray Al guys want to comment?IMHO, for any arc process, the longer the arc, the more spread out and diffuse the arc is, the diameter of the arc increases rapidly with increased arc length.  The long arc is very inefficient as the power density around the outside of the arc becomes so low it does not produce melting, only generalized heating of the base metal and surroundings.  A short, small diameter arc is more directional in it's melting, so the puddle is more controllable.