Welding aluminium with a mig - HELP!

[Supercharged Nat]

ok so im trying something new, ive got some mig wire (aluminium)and some argon gas and im trying to weld an inlet manifold, BUT its not working ive tried all the wire speeds, gas flow rates and power settings but i still get the same result.

I get blobs of weld than drop off the manifold and burn me feet. the blobs that dont run off once cooled can be picked off with pliers.

 

basically the wire isnt fusing with the manifold. Ive tried to weld a piece of sheet and it wasnt too bad, i managed to get a bit of a beed going and good penetration.

 

whats going on with the manifold? ive even tried heating it with a blow toruch first but still no good!

 

I need help please!

[Vista]

I've never done any MIG aluminium welding so can't really comment with anything that's going to be of much help to you. I learnt gas, stick and TIG welding as part of my craft apprenticeship and welding aluminium well is about as hard a job as there is. With TIG welding ally, Speed of advance, current flow and distance of the arc from the job are all critical.

 

edit: Just reread your message, bearing in mind I've never done MIG welding, it sounds as if you're not getting enough heat into the job for the weld wire to melt and fuse with manifold you're trying to weld. It's because it's not fusing with the parent metal that the weld blobs are picking off. It may be that the rest of the manifold is large enough to act as a heat sink and draw all the heat away from the area you're trying to weld

 

edit edit: I also recall that aluminium needs to be very clean before a weld will take, have you removed any oxidation from the surfaces of the job?

[bmxdave]

I actually learnt on ally, although i havnt done it for about 2 years now.

 

You have to be very carefull in such a situation. It seems like you need far more heat as its getting lost around the manifold, but if you go too hot youll start putting holes in things.

 

Could you try heating the whole manifold up as apposed to the area your welding? It might take some of the heat dissipation away. Im sure you know though, be carefull not to warp anything.

 

And thats about the limit of my welding knowledge.

[Supercharged Nat]

hi thanks for your reply, i did try removing the top surface with a sanding disc first to make sure it was clean. i think your right about the heat thing- just not sure how to get it hot enough to do the job?- how would i go about heating the whole manifold up and keeping it hot while welding?

[pauln]

The instructions on my Mig welder were to use it on full wire feed speed for ally. I was welding a zetec sump which i cleaned the oil residue off and then wire brushed and sanded shiny (ally oxidises so you need to do this just before you start to keep it clean). Using the mig on full power (150A) i did a watertight job. Think you need to get a bit of practice in on some scrap ally first. On this sump I have welded ally plate to the cast sump and the quality varies, it is easier to weld the plate than the sump. Wire makes a difference as well the sip stuff does a great weld but is very soft and tends to jam while the clarke (machine mart) wire goes through the welder better but the weld is not so nice.

[Supercharged Nat]

Thanks i appreciate the comments, im going to give it another go.

 

did you heat the area your trying to weld or anything like that?

[pauln]

Thanks i appreciate the comments, im going to give it another go.

 

did you heat the area your trying to weld or anything like that?

 

I did't do any preheating. On the areas where I got a weep on leak testing I cut a V with a grinder and rewelded. When you weld thick steel you cut a vee and do more than one run of weld (ie build it up) since the ally is thick compared to steel sheet I treated the ally in the same way as i would weld steel plate with a stick welder. So weld clean up and weld again til it comes level. Oh a word of warning don't breathe the fumes or you will find yourself visiting the smallest room in your house more often than you planned.

[Supercharged Nat]

ah, erm, il go get a mask then.... lol.

 

ive been using a mask since i started, but i have experienced a bit of a light head!

 

well its working alot better than it was, im sure more tweeking will see it perfect, even with steel it took me ages to find good settings.

 

thanks for the help!

[pauln]

Well done and just one thing......

[Rick]

is it cause your welding a cast ally manifold?? same with trying to weld cast iron??

 

also i think you have to prime your surface with a stainless wire brush and not a steel one

[Supercharged Nat]

pics will follow! hopefully get them tomorrow.

[pauln]

i

also i think you have to prime your surface with a stainless wire brush and not a steel one

 

Correct, forgot that

 

Cast ally is'nt brittle in the same way thay cast iron is but it's nots as strong as rolled plate ally. When you are welding it you can see the two types of ally flow together. The wire turns to molten metal so when it cools it's like a casting.

[Rick]

i wouldnt mind having a go to be honest iv only ever used those blow torch sticks which are a bit pants at actually joining stuff, only good for filling holes.

 

do you need a powerful mig to do it?

[pauln]

i wouldnt mind having a go to be honest iv only ever used those blow torch sticks which are a bit pants at actually joining stuff, only good for filling holes.

 

do you need a powerful mig to do it?

Mines a 150A and I used it at full power on my sump. Its strange because you would think that melting at a lower temp than steel you would need less current with ally. I had to do a couple of runs inside the sump to make sure I had a full thickness weld but if you can only weld from one side you will need to chamfer edges and build up the weld layers.

[d2000ad]

I dont think anybody pointed this out yet but if you are trying to weld aluminium make sure your mig welder has an A/c setting as you need that type of current to weld. You want to preheat the area first clean it with a stainless steel brush and if it apiece that has thick and thin parts of metal fairly close to each other you may want to post heat aswell to avoid cracking. Get your self some scrap aluminium to practice on as you will see that when you weld aluminium you have to travel at a greater speed than you do when weldind carbon steel or stainless. Hope this helps mate and good luck.