struggling with alluminium

[Carsten S]

4043 , okay thanks i shall give it another go tomorrow, what freqency balance is good? like 70?

Frequency control is probably how much DCEN/DCEP you have, not the frequency it self. Some welders show the number backwards, ie. 70% on one machine would equal 30% on another. Try the outerpositions on this knob, you will clearly see the effect. My guess is that 70% is DCEN = weldingpower, and 30% DCEP = cleaning. The more cleaning you choose, the more heat is going to your tungsten/torch.

I've usually run between 100 Hz and 120 Hz, ~80% DCEN. I use 5356/AlMg5 fillerrod.

 

[matt1978]

Frequency and Balance are not the same thing. Your describing AC Balance.

Frequency is how many cycles in Hz that it switches from Positive to Negative

Transformer types are usually fixed at 50Hz but most machines can be adjusted from 30Hz to 200Hz

Higher the number the more constricted the arc will be, but it also gets more noisy. Higher frequency typically used on thinner material but around 60-80Hz will cope with most things

 

[Carsten S]

Sorry - Should have pointet that part better out.

 

[jonnyBMX]

ahh yeah no worries i allready know the different between frequency and the ac balance, ac balance is pretty much how long of the time the torch is positive and how long is at negative, the longer the torch is positive the more cleaning effect you get but the more the tungsten will heat up and visa versa, i think i just need to mess about.

also i tried a few fillet welds but most of the time i cant get it to melt both sheets but only the bottom, or if i try the upright sheet it just melt, any suggestions here :S?

 

[Carsten S]

What settings, plate, gas are you trying with?

 

[jonnyBMX]

3mm ally plate (not sure on the grade) 100HZ, 60% DCEN, 2.4mm tungsten electrode (the while kind) puresheild argon gas from boc, 145 amps but using foot pedal. 4043 filler rod both 1.6mm and 2.4mm

 

[Ed.]

also i tried a few fillet welds but most of the time i cant get it to melt both sheets but only the bottom, or if i try the upright sheet it just melt, any suggestions here :S?

It sounds like you might need to remove the oxide off your aluminium using a clean stainless wire brush over all the edges to be welded and then after you brush it, wipe it down with pure acetone to clean it just before you try to weld it.

 

[jonnyBMX]

okay i will try with some acetone because i have been using a S/S brush that is only used on aluminium!

 

[Ed.]

The reason for the acetone is that sometimes the aluminium may have a slight oil film or gunk on it, and when you use the S/S brush to scratch away the oxide it can also just smear that oil and oxide dust around which will remain.

TIG welding metal needs to be really clean and both surfaces and all edges need to be oxide free, that to me seems the most likely cause of why the arc melts on one surface of the ally only and the weld pool doesn't wet over to the other edge, ensure that both pieces are earthed too and no gap between. If there has to be a gap then make sure that you earth both pieces so that the arc can hit both surfaces and not favour one over the other.

Lastly when I say pure acetone, I do not mean something like nail polish remover which has acetone in it ( and also oil ), you should also be able to use metho as well.

Hope this helps, just my 2 cents worth.

Cheers

Ed.

 

[jonnyBMX]

when you say earth both bits... how is this possible with only one earth from the machine? ( sorry if this sounds stupid) ive always just earthed the table and then welded metal ontop of the table

 

[Ed.]

As a very simple example, say you were doing a weld that required welding thick pieces of ally with a gap and one of those pieces was on the table and the other raised off it slightly, only one would have an earth and the other not, so putting an arc to it would result in the power to go to the earthed one as there is nothing to entice it to jump to the unearthed one, so you can always support/space it by clamping it by some means to a metal frame or support that was earthed to the table, or putting a metalic seperator in between the plates to earth to each other at least till you got a tack in on one end connecting the two pieces, once the tack is in place then both pieces are earthed. Alternatively you can get a short heavy cable with two clamps and use that to connect the two pieces. However I don't think that this is your problem and I think it is the following.

If you are welding thin pieces then chances are that they will be touching anyway and therefore both should be earthed, however if only one piece is brushed and clean, and the other not, then when the arc hits the two pieces it will melt the cleaner piece but because Aluminium Oxide has a much higher melting point/electrical resistance than clean aluminium, the oxide will stop any molten metal from sticking and blending in to the unclean one.

So if one piece has an oxide layer it will force the electricity to flow to the path of least resistance and therefore most of the power will go to the cleaner piece. I was doing a continuity check on a boats aluminium duckboard and the sterndrive leg today with a meter and just touching the oxide coated parts the meter would not sound with having to press harder on the multimeter points, but as soon as it contacted clean ally it sounded as soon as the probe tips touched.

This is what I think is happenning to you. I did the same thing when I first started TIG welding, if one piece wasn't clean I could see the arc melting the clean piece but no amount of encouragement would get the uncleaned piece to blend in with the weld pool. Eventually it would melt but by that time, the bottom bit had melted away and eventually when it did, it looked like there was a skin toward the arc side which is the Oxide layer and the back had melted first.

As soon as both pieces were clean, the weld pool just fused straight away to both pieces instantly, it was like chalk and cheese, instantly obvious.

I don't know if I am explaining this properly but I think that once you clean up both edges properly then you shouldn't have this problem. Again this is just my 2 cents worth.

Cheers

Ed.

 

[jonnyBMX]

yea i will try this again tonight, but i have made sure that i have properly cleaned thew surfaces before but just to make sure i shall check this again tonight,

thanks again

Jonny

 

[hotrodder]

also i tried a few fillet welds but most of the time i cant get it to melt both sheets but only the bottom, or if i try the upright sheet it just melt, any suggestions here :S?

If you haven't already read this thread... http://www.mig-welding.co.uk/forum/showthread.php?t=33791

While it's true you can't get ally too clean* that's very unlikely to be the root cause behind your problems with fillets IMO. You could clean it for days and use two return clamps the arc will still tend to favour one piece more than the other/dance between 'em if your arc length is too long (not a pop at Ed as those things can make a difference and as he said once it's tacked it doesn't misbehave as much). Thread on arc length here, note the two weld pools that resulted with the excessively long arc length... 'leccy will take the shortest route which with a fillet weld can be the sides (the joint is at the apex of an imaginary triangle). With AC the polarity is changing many times a second giving the arc more posibility to 'change it's mind'


* It is a bit easier if it's spotless but not night and day. Personally speaking any marks from a stainless brush on any of my sheet ally work (new material obviously and plastic protected sheet) means i've screwed up and had to brush the crud out. I only bother cleaning things with brake cleaner because any source of hydrogen (oils, grease, moisture etc) = hydrogen porosity. Even then it depends what you're doing... if it's decorative, not gonna see any stress etc then i usually peel the plastic off and weld it.

If you're solvent wiping stuff don't forget the filler wire and despite what the interweb claims brake cleaner won't necessarily kill you, it's chlorinated solvents that potentially create phosgene (WW1 nerve gas) if you're daft enough to strike an arc while the part is still wet and in the UK brake cleaner will almost, if not, always be 1. chlorine free and 2. have something like 'contains no chlorinated hydrocarbons' or words to that effect written on it. MSDS sheet will confirm but i've yet to see a tin of the stuff that's chlorinated

 

[jonnyBMX]

well, num nuts here ordered a gas lens... but forgot to put the ceramic into the basket and i dont want to have to pay £6.70 postage for a bit of ceramic so no gas lens for now untill i need to buy something worth paying the postage on (local welding shop didnt have any either)

thanks for the link hotrodder, i also think its more an issue with my techniquie rather then the metal haha will give it more practise tonight going to need a new bottle of argon soon too! gunna just get a W size one from BOC the Y was good but while im learning need lots and lots :P

 

[justmental]

2 gas lenses from weldequip only cost me £6.15.
if you order them in the morning you will have them next day.

 

[jonnyBMX]

yeah i got the gas lens, just not the ceramic so i gota pay a standard £6.70 postage for one ceramic lol!

 

[julieanncharters]

got half way thru an ali tigging job today all 6mm
when it started going to rat ****.
loads of oxide forming on totaly clean material.
after checking most stuff and much head scratching finally traced it to the water cooled torch was sending a very fine mist of water on strike up .
its fecked in the flexi bit.
always sumit to keep ya on your toes eh .

 

[chevy2]

yeah i got the gas lens, just not the ceramic so i gota pay a standard £6.70 postage for one ceramic lol!

I got a set of 1.6, 2.4 and 3.2 gas lenses, 3 ceramics and the white insulator from shopriver on ebay for around £15-£18? Delivered.

Only problem they take about 10 days to arrive.

 

[jonnyBMX]

okay thanks ill see what i can find :P

 

[pedrobedro]

yeah i got the gas lens, just not the ceramic so i gota pay a standard £6.70 postage for one ceramic lol!

Don't you have a welding supplier near you, I can pick them up for £1 locally.