Aluminium MIG welding.

[koba]

Anyone tried it?
Any good?

[The Pastor]

Depends on the skill of the welder, but its nothing hard

[pete376403]

I thought you could only successfully TIG weld aluminium, so I had a look around at a forum dedicated to MIG (!)
http://www.mig-welding.co.uk/forum/showthread.php?t=659
they are saying that DC (ie mig ) doesn't clean the surface oxides of the ally as well as the AC (ie tig) so it's ok for thick metal but not so good for thin.

[Shaun]

I just brought a Miler 250 unit, so I can weld alloy easy myself. TIG

[ManDownUnder]

Can gas weld it too with the right flux and filler. Bit of a bugger though - it tends to be good... good... good... good... HUGE HOLE!

[The Pastor]

I thought you could only successfully TIG weld aluminium, so I had a look around at a forum dedicated to MIG (!)
http://www.mig-welding.co.uk/forum/showthread.php?t=659
they are saying that DC (ie mig ) doesn't clean the surface oxides of the ally as well as the AC (ie tig) so it's ok for thick metal but not so good for thin.

(its called ac mig for ali mate)

[Sensei]

Have been welding for close to 30ys now , ally is not as easy as everyone thinks be it Tig or Mig etc , alot can go wrong very quickly if you don't know about Ally & the types you are trying to weld . My 2Cents worth .

[pete376403]

(its called ac mig for ali mate)

Ok, thanks. My only experience of electric welding was on a block course while doing the apprenticeship (a long time ago). The welding tutor called it "tig" for tungsten inert gas so thats what it's been for me, and I do recall how he said the unit started on AC to break up the surface oxide and then switched to DC. Things may have changed in the interim 34 years.

[CookMySock]

I saw an inverter MIG welder on trade me that would do ally. You just told it your panel thickness and the rest was automatic.

Steve

[AllanB]

Bit of a bugger though - it tends to be good... good... good... good... HUGE HOLE!

Hmmm reminds me of an old girlfriend......

[Pussy]

Ok, thanks. My only experience of electric welding was on a block course while doing the apprenticeship (a long time ago). The welding tutor called it "tig" for tungsten inert gas so thats what it's been for me, and I do recall how he said the unit started on AC to break up the surface oxide and then switched to DC. Things may have changed in the interim 34 years.

There is TIG and MIG alloy welding. For tig, it is continuous AC and high frequency.
For MIG, it is wire feed DC
Argon is used as the shielding gas in both cases, although in the US they use helium as the shielding gas.
Almost anyone is able to make a weld with both methods, but it takes considerable experience to be good at it

[no-coast-punk]

The problem with MIG welding is that the process requires far higher current than TIG welding.

Current = Heat

MIG welding basically turns the wire into a plasma and then deposits the plasma on the material you are welding. This is also why MIG welding is always DC current. The current has to be flowing from the torch to the work otherwise it would try and suck material off the work and deposit it on the torch.

TIG welding uses the electricity to get thing hot enough to melt and you deposit liquid metal by hand using the fill rod.

Problem with Al based materials vs. Fe based materials is that Al materials

a) Have a far lower melting point
b) Absorb heat much more readily

If you are working with very large bits of metal that can act as a sufficient heat sink, MIG welding works just fine. However with smaller pieces it blows big holes in stuff with a quickness.

Another disadvantage of MIG welding is the enormous temperature gradient it creates within the crystalline structure of the metal. This gradient makes all the molecules get all wonky for a bit. This results in an EXTREMELY hard structure (much stronger than the original metal) inside the weld bead transitioning to an area that is slightly weaker than the original metal less than 1mm away from the weld back to original properties a bit further away.

With steels this isn't really a problem. You are working with pretty strong stuff and the weak band is very small. With Aluminum this becomes a BIG problem because the heat absorption means that the band of weaker metal is far wider and Al was never strong stuff to begin with.

The reason we use He over here in the states instead of Ar is because of our incredible superiority at everything (extremely kidding, we just have huge He deposits which makes the stuff cheap and available). It's a heat/contaminant management thing. A bunch of the heat and liberated nasty gasses from the metals will get dumped into the shielding gas during welding. He is lighter than air while Ar is heavier than air. He will float away carrying heat and nasty stuff away. Ar will have a tendency to just sorta sit there and not carry things away as effectively.

[GSVR]

Anyone tried it?
Any good?

I have and unless your doing production runs I wouldn't bother.

Its not a matter of just putting alloy wire in. You can't use a sleeve thats been used for steel wire. Ally wire is soft and doesnt like being pushed so a tractor handpiece is the way to go. Etc Etc.

Tig is way slower but you have so much more control and cleaning/pulsed waveforms to play with. You actually need quite alot of power and any good TIG ally welder is ussually 3 phase.
I didn't bother buying a TIG capable of alloy for home as I would have had to have got a serious single phase outlet put in.

[koba]

Cheers all,
I dont think I will bother. For now at least.
I have TIG welded aluminium before, It is hard as Sensei says but I found I was OK at it with a really good welder with a nice foot control. As those who have had a good poke at it will of course know it has a real fine heat range where it is all gravy. I love it tho and found the contol interesting and challenging.
Great fun.
Unfortunatley I don't have ready access to such a machine (Shaun - ENVY!)
so was looking at the MIG setup as somthing cheap(ER) I can have easy access to but a mate has offered to do the engine mounts that need sorting so that will tie me over for now.

[old git]

yep, it can be done, but you need a spool feeder close to the handset as it jams up in a long lead...............not for the feint hearted as its real easy and quick to make a mess!