Mig or Tig ?

[Dyno6942]

There is a statement in the 2012 Alweld Boats brochure reading: "Tig welding produces a leak-proof seam, which Mig welding cannot." Can someone verify this?

 

[Quackrstackr]

Bunk.

Any weld is only as good as the prep and the person or machine doing the welding. TIG can have just as much porosity as anything else.

 

[fabricatorbob]

Both mig & tig welding can produce a leak free weld. I agree prep is important,also setup and skill are just as important. For example just lifting the tig torch too soon after a weld is completed, will almost always leave a pin hole. With some skill, the proper voltage and wire speed settings and the proper shielding gas i weld a leak free 20 gallon fuel tank in about a half hour with the mig. That same tank takes me almost an hour with a tig welder.

 

[Dyno6942]

I've been a steel fabricator for 35 years. I've welded alot of steel. I've welded aluminum with a Mig (spoolgun), but I've never had a Tig gun in my hand. I wouldn't be welding on the hull, just going to be framing the decks out of aluminum, and was just wondering if a spoolgun will get the job done?

 

[JMichael]

The guy that did the repairs on my transom used a spoolgun. I'm not a welder but after watching him do my repairs and seeing the results, I would say you could certainly use a spoolgun to build decks with.

 

[ckr74]

I think most of it has to do with personal preference. I personally get better results with tig. Mig is much faster though. I can use either.

 

[PSG-1]

Provided that you are dealing with new material, you have the proper joint fit-up, and you've taken the time to properly clean the material with a clean SS wire brush.....aluminum welds like a breeze with MIG, and produces water-tight welds.

Now, if you're dealing with some oxidized material, TIG is the way to go, because you can 'burn out' the contamination (heating, then wire brushing)

Because TIG allows the independent feed of filler material, when you come to a bad spot, you can back off feeding wire, until the contamination burns off, then you add more wire.

With MIG, if you hit a contaminated or oxidized area, the wire continues to feed, producing black 'popcorn gobble' or 'chicken sh!t' as we refer to it around here. :mrgreen:

Also, TIG is MUCH slower than MIG. If you're doing precision welding, TIG is the way to go. But if you're doing a lot of high-production work, MIG is the answer.

 

[bassboy1]

Also, TIG is MUCH slower than MIG. If you're doing precision welding, TIG is the way to go. But if you're doing a lot of high-production work, MIG is the answer.

Along with that, because TIG is much slower, the net heat input is much higher. As a result, on long seams, say hull seams, distortion becomes a much greater issue with TIG than with MIG.

They both have their place. Trying to pick one or the other as 'better' is foolish, as certain jobs really cater to one but cannot be done with any practicality with the other and vice versa.

But yes, that statement from Alweld is horsecrap.

 

[PSG-1]

Very true about the heat input and distortion with TIG. Especially when it comes to aluminum. As with any type of sheet metal welding, lots of tack welds are required, and sometimes, you even need a jig or fixture to control warpage.

A lot of people don't realize that in addition to having a melting temp roughly 1/2 that of steel (1217 F vs 2750 F) aluminum has 3X the thermal conductivity of steel.

This makes it totally different than steel welding. With steel, you set the amperage and run with it, and that amperage works throughout the entire weld.

With aluminum, the amperage setting will be OK when you start out, but as you progress and the material heats up, the setting becomes too hot. This is where the foot pedal comes in handy, to vary the heat, at least with TIG welding. Using MIG, there's no foot pedal, so, the operator might have to break arc, let it cool down, then, run another bead, to prevent the puddle from sagging and blowing out.