Some help with aluminium please

[tab]

evening all

i've read many threads on here about aluminium welding and watched lots youtube videos on it but still having a few teething problems.

been practicing with mild steel for quite a while now and feel confident with it, most joints, thicknesses, vertical etc etc so thought i would have a go at some aluminium.

now i think i may have started running before i can walk really with this as i've gone straight in with the joints rather than starting by laying beads and progressing my way up as i did with mild steel, but i thought it would be the same technique so thought i'd give it a shot.

problems i'm getting seem to be controlling the weld pool, as it not really getting it flowing, then when i thought i did (flowing smooth, consistant looking beads) when tested it had no penetration.

next i tried a few more amps (well put my foot down a bit more as i was using a foot pedal) and just seemed to burn though or roll the edges back.

i've attached a few photos to show what i'm on about, any advice is appreiciated even if its telling me i'm doing everything completely wrong.

so now for the technical details,

welder set to AC, no pulse or anything like that
max amps set to 150 using foot pedal to control but never fully depressed
1.6mm zincoriated tungsten, ground to a point
gas at 12lpm, set with flow meter on bottle checked with pea shooter at torch

material is 1.6mm box and i also tried to attach some 3mm flat bar to it to cap the ends off, bought new, wiped with meths and cleaned with a designated stainless brush.

thanks in advance for your help

 

[Frosty]

Your aluminum is filthy! Do you have a grinder? If not, get one! Buy a crimped, not knotted, stainless wire wheel 4"-4 1/2" and use that to clean your edges your going to weld. Thats half your battle. Once everything's clean, you seem to have good travel speed on your first two pictures except toward the end, you either slowed downed or touched the material or filler rod, lots of soot.

If you keep burning thru on the box at the ends, put some heavy tacks there and then melt into them. It will be nice and will have a cleaner look.

Your other pictures on the fillets seem to have the torch pointed up on the top part of the weld. I tend to point the torch down until its good and wet then move up. Heat rises, so the top part of the fillet is already getting good and hot by melting the bottom of the fillet first. Then watch how its fusing at the top and bottom and add filler accordingly. You'll tend to favor the top for the filler as gravity is pulling the wet puddle down. Hope this helps.

 

[hotrodder]

You should be able to pretty much halve your gas flow for a start. Should rarely need more than 7 L/min. Then read this thread (or if you already have, read it again)... http://www.mig-welding.co.uk/forum/showthread.php?t=33791
Ally isn't more difficult than steel but it is quite different. Spending a little time running beads on plate to get a feel for the way weldpool behaves would be worthwhile imo.

If your arc length is right you shouldn't need to manipulate the torch pointing it up and down, especially when the material is 1.5 - 3mm thick.

 

[Ed.]

Hi, I am not an expert TIG welder as I mainly use MIG but have been doing TIG for about 16 mths, so take this for what it's worth, the Ally tig projects I have done in aluminium have been from 3mm to 6mm and on the 3mm I don't need to go past 80A. You may need a bit more if the ally is sitting flat on a steel bench which acts as a heat absorber and less if it is in the air, for the 6mm I have gone up to 160A and all these have been with pulse which has less heat than no pulse. I also don't use a foot pedal although I do have one lying around somewhere.

So I suspect that is the reason why your ally is melting away quickly (too many amps) as for the contamination of the gas, check that your hose and TIG torch isn't leaking somewhere and sucking in air. My gas setting is usally about 7-10lt and never had a need to go higher than that. Just my 2 cents worth.