TIG or MIG for Aluminium?

Discussion in 'Metal Boat Building' started by ted655, Oct 20, 2005.

  1. ted655
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    ted655 Senior Member

    For welding aluminium heavy gauge & plate, which is a better method, TIG or MIG?
     
  2. lewisboats
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    lewisboats Obsessed Member

    MIG for ease and speed, TIG for accuracy, controlability and less distortion. TIG is much more difficult to master...unless you have experience in gas welding, to which it is very similar. MIG will tend to give you a surface weld with less penetration unless you are fairly well practiced in the method. The best way to find out is to try them both and see which works best for you.

    Steve
     
  3. Wynand N
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    Wynand N Retired Steelboatbuilder

    Infact, TIG is notorious for distortion - either with steel or aluminuim - more so on thinner plate. This is due to the excess heat dispersion into the plate surrounding the weld because of the slow progress with TIG. That said, TIG is the better quality weld if done by a competant welder.

    The norm in the industry is MIG
     
  4. cyclops
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    cyclops Senior Member

    What % gas mixtures are best for common marine Aluminum jobs?
     
  5. marshmat
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    marshmat Senior Member

    A skilled welder with a good TIG machine is the best way to go for aluminum plate. MIG is easier to learn, but it's not easy to get a MIG to weld evenly through a thick plate; it tends to stay shallow unless you've got a lot of skill with it. So TIG for better quality, MIG for less experienced welders. Or so I understand it....
     
  6. scormack
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    scormack Simon Cormack

    I am not a welder but I have been involved in a good few alu boat building projects. All recent projects have used a synergic mig which is quick, limits distortion and relatively easy. Problems are the cost of gear and for some reason I don't understand units from certain manufacturers don't seem to work as well, one yard sent back their new unit and bought from another manufacturer and had no problems, this is on 4 to 10 mm plate.
     
  7. Wynand N
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    Wynand N Retired Steelboatbuilder

    Personally prefers Heluim gas....for the welding though
     
  8. Jeffscarstrucks
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    Jeffscarstrucks New Member

    Hi, New here but this seems like a great site. I just finished a floor frame for an aluminum Roamer and used a Miller spool gun (MIG) and it worked out very well. Argon is the normal gas for this process. I do like to use TIG for smaller more precise work but MIG is more of a "production" speed if you are doing a lot of work over .125 or so. There are a lot of variables to consider when choosing a process or gas combination when welding aluminum and no one answer will ever cover two jobs. I frequent Millerwelds.com forum (AskAndy under the motorsports sub heading across the top of the page). There are many knowledgeable folks there. I am looking for a Piece of Miller equipment but that will be another post. Good Luck, JEFF
     
  9. quality welding
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    quality welding New Member

    i new to this site , with that said i've welded with miller is the best welding machine.the best way to tell what you need is to answer a few questions . 1. are you doing a hull or some parts on a completed hull ?the stringer system you can use mig mig stsnd for metal enert gas and co3 is the norm for steel .aluminum us 75/25 mix argon -helium mix sometime you can use straight argon depending were you are located . hardly anyone use straight helium anymore . miller spool guns with the 2pound spool in the gun is good for feild work . and 15lb spools on a cart with 6ft mig gun works great in a shop . miller 350 power source can be adapted for both . i prefer the 250 sycrwave becauce its about 3000.00 verse 4000.00 or more for the 350 sycrowave . they also have a 300 trail blazer that will work very good on remote locations an in the shop its about 3200. us plus all you have to add is high freq and mig attachmnet or tig leads an ground hope this helps good luck.
    ps. distortion has a lot to do with over heating youtr project or poor fit and gaps . one of thr best way to prevent destortion is to have welding your project in right order try no to heat the the whole project up at once . jigging up your project to hold it in place helps alot example jig frame antack it in atleast evry 3-4 inchs with 1/2" tack on on side . then go on the other side an tack it agin. if it round or brace tack at least least 4 places around it that way when you fully wel it the destortin will pull it back to it origanal angle.
     
  10. ted655
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    ted655 Senior Member

    Thanks everyone! I have a son, going to welding school now. I needed to know where to concentrate his efforts. I also will be the one who decides what equipment to buy. He already knows he doesn't want to pipeline & later (next year), he will have the choise to decide which path to follow. This info helps. Again thanks. Ted
     
  11. saeble
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    saeble Junior Member

    whatever you do, do not use 'regular' MIG gas. Aluminium seems to be very fussy about shield gases, only use the 100% Argon and not the mixes used for steel work.

    outside of that, be careful with heat. Whilst it may be an urban myth there is a local story about a guy who built a large cray boat (10m) and it survived only 6 waves before it blew into ribbons. The cause of the failure was the Aluminium being grossly overheated and the sheet breaking away from both sides of the weld. While I would imagine a failure wouldnt be as spectacular as 'blowing into ribbons', you could have serious problems if you get your heat control wrong.
     
  12. mungral
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    mungral Junior Member

    welding Aluminium general info.

    if your welding thin Aluminium, say, under 3mm thick and you dont have to weld very long runs. say under 1 meter in length use TIG.

    for Aluminium over 3mm thick use MIG.

    allways use 100% Argon gas

    if you have a MIG welder that can be programmed, talk with the guys that make the welder and get them to set it up for Aluminium. (some times they may need to change a chip to get the best results)

    If your welding Aluminium plate over, say, 6mm and its in a high stress area. do a TIG root run then a MIG capping run.

    when welding stringers onto the shell plate (or any flat'ish surface) stitch weld the stringer on instead of fully welding it. stitch welding for people who dont know is welding for a set distance e.g. 50-100mm then leaving a 50-100mm unwelded gap then 50-100mm of weld and so on.

    all ways fill the crater left in the end of your welds. as this is the main place cracking will start.

    use a darker lense in your welding helmet than you would for mild steel

    if the weld looks like its just sitting on top of the Aluminium then turn up your amps (make it hotter) if the Aluminium suddenly falls on the floor then turn your amps down (to hot)

    do not get any oil based products on the Aluminium before welding because the weld will not stick at all. (this includes thick black marking pens which are really great for drawing on Aluminium)
    a good sand with 80 grit disc sander of the area where your just about to weld never hurts.

    hope this helps
     
  13. ted655
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    ted655 Senior Member

    Very much, thanks
     
  14. mungral
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    mungral Junior Member

    stich welding example

    Tought this may explain stich welding a bit better

    pic shows a typical stich welding setup. shown in plan view
    the thin horizontal line in the middel is the stringer.
     

    Attached Files:


  15. rugludallur
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    rugludallur Rugludallur

    RE: What % gas mixtures are best for common marine Aluminum jobs?

    If you live in the US where Helium is cheap go for Argon/Helium or even pure helium for better heat transfer, if you live anywhere else where helium is 10x more expensive go for pure argon.

    Yours

    Jarl
    http://www.rugludallur.com


    Quote:
    Originally Posted by cyclops
    What % gas mixtures are best for common marine Aluminum jobs?

    Personally prefers Heluim gas....for the welding though
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    Wynand Nortje

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