What gas do you like for Aluminum?

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I haven't TIG welded Aluminum in about 4 years but thinking back I believe I used straight Argon.  What do you guys usually use for both MIG & TIG and in what cases do you change the gas ratio with Helium or possibly other gases?  Is there a preference to some extent on certain gas mixtures or are any gas changes done solely to meed welding codes?I will be building an Aluminum River Jet Sled boat and will be TIG welding the entire boat except for some stuff like the hull seams and tacking.  Although I may TIG the seams as well so I know the weld is solid.  I don't trust my MIG welds on Aluminum yet as i've only done it once back in college years ago and I burned through on my first try, gave up and fired up the Syncrowave and continued TIG'n.  Any MIG welds will probably be done by a buddy of mine who used to work at the shipyard I am employed at currently and is the best Aluminum MIG welder I know.  So I trust him on the seams, but I am debating on whether I want to do the project myself 100% as a self satisfaction thing if you know what I mean.Anyways, just wanted to know what you guys use and why.
Reply:Straight argon, unless I have some really thick material, then I would add a little helium for a hotter arc.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:Straight argon for 99.99%.  Helium mix only comes out in the blue moon that I've got to do a 100% pen, multipass weld, like repairing an aluminum engine block.
Reply:I weld on 3-5 mil and 15 mil Alum. all day.  And we use Hel/argon mix on all of our welds.  Argon is used for SS.
Reply:Straight argon for both TIG and Mig on aluminum.I use 98% Argon, 2% O2 to spray on SS (single pass).  For heavier material using multipass, I use tri-mix.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Welder Boy,Think you're going to find that, depending on the gauge material you're using, the mig (without pulse) is difficult to use on light material.  Now if your buddy's got a MM350P, we're talking a different story.I would definitely try some scrap material before I decided how I wanted to approach the job.Anything less than about 1/8" I generally leave the spoolgun (MM251 w/30A Spoolgun) alone and reach for the tig.Just my .02Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Sundown, looking at blueprints of boats similar to the one I am designing shows little if any 1/8" material.  Much of it is 3/16-3/8" which is why I considered both welding methods.And regarding your comment on pulsed mig, My friend actually does pulse aluminum MIG manually so it may be possible.  He was taught at a few places he worked for by some veteran AL welders and his method is very smooth and fast.  But when he got to the shipyard I work at now he was told to stop that method because the welding foreman couldn't assure that his welds were sound with that method.  So I am not sure if that is the route I want to go or not.Like I said, still in design.  So I have time to work these details out.
Reply:WelderBoy,If we're talking material of that thickness (3/16-3/8"), I'd definitely go with the mig.  That's exactly the range where a MM251 with 30A spoolgun will excel.  Would not need the pulsing.  TIG would be way too slow.I have not heard of problems using pulsed mig on thin gauge aluminum.  In fact, that's about the only way mig can be used on very thin material.  In the shipyard, I doubt they have much experience with the thin gauge material used in a lot of "recreational" boating.  When using heavier material there's little advantage to pulse, except for out of position welds.Sorry, didn't realize how heavy a material you were talking about.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by WelderBoyMy friend actually does pulse aluminum MIG manually so it may be possible.
Reply:I have spent time building aluminum jet boats for Northwest Jet Boats and what we have done is mig the inside joints like bottom-side, bottom-transom, and side-transom then tig weld it on the outsides. You can run pretty hot (22v). The side-transom joint is typically welded with a stringer weld, then another pass with oscillation. Then tig welded on the outside later in the process. The reason for the stringer weld is to get it together quickly and without warpage, then with more material in the corner, you can put the heat to it with some ocillation. These are very tough boats but it is a rare occasion that we use 1/4 or 3/8 material in them. Most bottoms in the industry are 3/16. Some do request 1/4 but usually isn't necessary unless you plan on banging big rocks. You will find .160 bottoms on cheaper boats. Hope you post pictures of your build.Bil[url=]
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Reply:Ya, the boat will be running in water as shallow as 6" and will often hit rocks and stumps when going from hole to hole.  The bottom needs to be very sturdy.  The entire boat needs to be very rigid actually and will be supporting up to a 200hp Jet Prop outboard.  I've seen poorly built river sleds that twisted like a piece of paper with every turn or wave in the water.   I do not want that.Here are some similar designs I am looking into mimicking.  I have the boat designing cad software and have been tinkering with designs.http://www.treasuresandstuff.com/alumriversled.jpghttp://images.craigslist.org/0101050...03960090f4.jpgSee why it needs to be tough?http://www.northriverboats.com/image...scout4_lrg.jpg
Reply:Originally Posted by olddadHow does he "manually" pulse with a mig ? Does he have a pedal rigged up, is he trigger welding, does he vary his stick-out ?How do you manually "pulse" with a mig without a pedal, inquiring minds want to know.
Reply:partagas,Can't imagine why your company's using a helium/argon mix on 3mm material.  Sounds like a waste of money to me, aside from the fact that there's a lot more heat there than needed.I was taught and everything I've read, that you only need to go to the 65% Helium/35% Argon for aluminum 1"-3".  75% Helium/25% Argon for material thicker than 3".Maybe you could shed some light on why they use that mix.  I would say that goes against the "industry standard".Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by WHughesThese are very tough boats but it is a rare occasion that we use 1/4 or 3/8 material in them. Most bottoms in the industry are 3/16. Some do request 1/4 but usually isn't necessary unless you plan on banging big rocks.
Reply:Any time I tried to "pulse" a MIG aluminum weld with the trigger, the puddle just turned to a pile of black poop. Even when using the pulse adapter on my Esab MM260 w/spoolgun, it doesn't seem to weld better. It LOOKS nicer, but does not penetrate as well. I've had the most luck on aluminum with no pulse.Crank it up hot and be ready to move at ludicrus speed.
Reply:I could not tell you what "industry standard" is, as this job is the first I have had working with Alum.  As for waste of money, I say that everyday.  But when you work for a multi-billion dollar company, you do what they say.  All I know is that I build a giant thermos that has a big magnet in it. Originally Posted by SundownIIIpartagas,Can't imagine why your company's using a helium/argon mix on 3mm material.  Sounds like a waste of money to me, aside from the fact that there's a lot more heat there than needed.I was taught and everything I've read, that you only need to go to the 65% Helium/35% Argon for aluminum 1"-3".  75% Helium/25% Argon for material thicker than 3".Maybe you could shed some light on why they use that mix.  I would say that goes against the "industry standard".