Tig aluminium woes

[Daniel Brannan]

Hello

I know this must come up all the time but I’m stuck with tig on aluminium. I’m not a total noob at this and have managed to attach bits of aluminium to each other in the past with an amount of success.

Anyway I have been trying to weld a brace plate into a subframe as per these pictures which you can see is just awful. Full of porosity, messy, it’s sagged in places and I’ve actually warped the whole piece:

Not happy with this, I thought I would do some practicing on bits of plate clamped into a fillet but I couldn’t even tack weld them together. When hitting the root with 185 amps a puddle would barely form and after forcing some filler in there I got 3 horrible yellow black and green tack welds which a stiff breeze would blow over:

I had cleaned everything with dedicated stainless brush and then solvent wipes first, including the filler. The plate is 5mm thick 6082t6, tungsten is 3/32 (2.4mm), gas flow is around 30cfm pure argon. Filler is 5356. Ac balance is set at around 35-40 percent and is enough that the tungsten balls slightly when given some decent current.

I don’t really understand where I’m going wrong unless my gas is contaminated or not flowing as much as my gauge reads but it hisses pretty healthily when I trigger the pedal.

Any suggestions welcome

Regards

Dan

 

[JOEPRO]

Hi there,

None of the photos are showing just Dropbox links.

You are better to upload photos directly to the forum software from your phone.

 

[Daniel Brannan]

Ok I figured it out

 

[voipio]

30cfm is about 850 litres/min, which is way, way too high a gas flow. Around 6-7 litres/min would be closer to the optimum. Is the gas flow scale being read correctly? I'm guessing it should be 30 cubic feet/hr, which is around 14 litres/min, which would still be on the high side.

 

[Daniel Brannan]

Sorry my mistake - my gauge says 30 cfn (whatever the n is) which is also around 14 lpm as you say. Would that be enough to prevent proper shielding?

 

[voipio]

Could it be 30 cfh? Where h stands for hour.

 

[Daniel Brannan]

Could it be 30 cfh? Where h stands for hour.

I think it might be a Chinese translation special

 

[Daniel Brannan]

Either way I will try your suggestion tomorrow and reduce the gas flow. I only increased it to 30 because things were going black but that could have just been my technique or lack of it

 

[BrokenBiker]

Sorry my mistake - my gauge says 30 cfn (whatever the n is) which is also around 14 lpm as you say. Would that be enough to prevent proper shielding?

general rule of thumb, whatever number is written on the ceramic cup, set the gas there as a lower limit and the cup number x 1.5 as the upper limit...so a no.8 cup, which is the biggest you will need for aluminum, gives you a range between 8-12LPM...a no-5 cup gives you a range between 5-7.5LPM...if you try running 12LPM through a number 5 cup you may find there will be turbulent flow out of the cup that sucks air in which will cause porosity of the weld and potentially also cause issues with the tungsten not being properly shielded. there is no need to go bigger than an 8 with aluminium as its a non reactive material so doesnt need a huge amount of shielding like stainless or titanium for instance, but a bigger cup gives a bigger coverage area which will widen the etched area around the weld. i use a number 5 on aluminium with 6LPM argon and a smidge more tungsten out than is technically correct, but thats just what works for me.

now, add to the gas issue, it also looks like you are welding a casting, which in itself is going to give you issues with crud floating to the top of the weld, potential porosity from trapped gas and inclusions of god knows what from the casting process. it could be a relatively clean casting, or it could have grains of sand (probably not in a production part like this, but it is something to consider with castings), oils, grease or other contaminants stuck inside cavities just below the surface. the trick there is to run slightly more cleaning action and do what is known as a cleaning pass where you dont add filler, just get a puddle going and move it across the joint to 'clean' the casting by floating the crud to the top, which can then be wire brushed and hopefully you can get some good clean metal to weld to. if you are trying to weld extruded aluminium to cast, i personally try and 'clean' the joint area with a pass of the torch before tacking the fresh material to it, but again thats just my personal preference.

im no expert by any means but ive tried welding cast ally and it was horrible stuff, and the advice given to me by a very skilled welder i do work for is the same advice ive given here.

 

[Daniel Brannan]

Thanks for the info. I just checked and it’s a #12 cup - great big glass thing. I bought this because I thought that would give a wider shielding coverage area.

 

[Popcorn]

You'll ideally need to pre-heat that as it's cast alloy, so it's full of crap. Also worth changing the filler rods to higher silicon content rods.
4043 or even better 4943 but they're hard to come by in this country, both these rods have Silicon in them which helps with wetting out the cast alloy.
A number 12 cup is more for stainless and other exotic metals definitely not needed on alloy.

 

[Daniel Brannan]

Ok thanks everyone. Plan of attack then - go back to sensible cup and 9lpm and see how it behaves.

What kind of current should be needed for 5mm thick plate fillet welds? My welder only goes to 200 and with the pedal for some reason maxes at 185

 

[chrismac]

Ok thanks everyone. Plan of attack then - go back to sensible cup and 9lpm and see how it behaves.

What kind of current should be needed for 5mm thick plate fillet welds? My welder only goes to 200 and with the pedal for some reason maxes at 185

there is such heat sink with aluminium welding its hard to give an amps, as mentioned above as a cleaning run, you could do a few passes of that as hot as you will dare, once you have the heat in the parts it should flow nicely, dont take the wire out the shield gas either, if you do you will be introducing dirty wire into every dab, keep the wire in and around the pool.

Good luck

 

[Daniel Brannan]

I’ve most definitely been taking the wire right out. The problem is you watch tutorial videos on YouTube and its a guy welding 2 perfectly clean plates of aluminium together on a clean table, in a well lit room with easy access to the whole part and usually sat down. Everything I ever want to weld is awkwardly shaped, or dirty, or cast or really small. I can never quite get comfortable or get access to do what I need to with the filler

 

[BrokenBiker]

Thanks for the info. I just checked and it’s a #12 cup - great big glass thing. I bought this because I thought that would give a wider shielding coverage area.

That's more designed or aimed at stainless. It will certainly give a higher coverage area, but it's not needed at all for aluminium

 

[BrokenBiker]

Ok thanks everyone. Plan of attack then - go back to sensible cup and 9lpm and see how it behaves.

What kind of current should be needed for 5mm thick plate fillet welds? My welder only goes to 200 and with the pedal for some reason maxes at 185

For 5mm plate you will need to start at max amps and possibly a preheat...my tig goes to 200 on the pedal and I struggle with anything thicker than 5mm in 1 pass and the larger the piece the more it will suck the heat away from the weld

 

[Daniel Brannan]

Ok so with a fresh head today I did as suggested on here and went to a smaller cup (7 is the biggest I have) and gas flow around 9lpm. I also turned up the cleaning action slightly. I managed to produce a cleaner looking weld:

As you can see, it’s a better colour now although I’ve still got gaps because I’m a crap welder, and it was getting too hot towards the end of the bead (left) so there’s undercut.

About the gas - I have a theory - the hose running from my gas bottle is only 3mm. I’m wondering if using the #12 cup and trying to turn up the flow was more than that hose could actually flow and so I wasn’t actually getting coverage at the cup?

It really is horrible stuff to weld. It doesn’t really flow rather it ‘blobs’. I also get times when the filler just balls up or when I just can’t get the puddle to go where I want and there’s a gap I just can’t fill but I then fear everything getting too hot and rush past it. And then finally when you get a half passable bead down you realise the whole part has distorted and is ruined anyway.

 

[Misterg]

About the gas - I have a theory - the hose running from my gas bottle is only 3mm. I’m wondering if using the #12 cup and trying to turn up the flow was more than that hose could actually flow and so I wasn’t actually getting coverage at the cup?

I think it's more likely that the gas was coming out of the cup too fast and creating turbulent flow that draws air into the plume.

(Correct flow on the left, too high on the right)

Only a hobbyist, but I try and avoid welding towards an edge in aluminium: Weld from one edge towards the middle of the part, then weld from the other edge back to join the first weld. Probably not correct, but I find it easier to manage the heat that way.

 

[BrokenBiker]

Regarding getting too hot towards the end, if you haven't got a pedal or are struggling to back off enough or quick enough, when the metal is cold, run a bead that starts 20mm from the end. A small bead like that wont get too hot and then you can weld up to the start of that bead just as its starting to run away on you.

Good progress though, that weld does definitely look better.

 

[Daniel Brannan]

I do have a pedal but often I try to back off and then go too far and end up with the puddle getting ‘stuck’