Basic Settings for Aluminium

I have a Nexus 250 AC/DC TIG Welder with a Pedal.
I have been welding for a couple of years now (Self Taught) and I think I have grasped Mild and Stainless Welding pretty well
I would like to try my hand at aluminium, I keep getting people asking me if I can do it etc.
I recently watched a Welding Video and tried some of the things out, like Clean, Clean and Clean again!
I did a few trial welds, but they were very hit or miss.
I think the problem is just getting the Welder settings somewhere close, I just guessed the settings.........
The one thing I was struggling with was a basic aluminium setup for my Welder
Anyone help?

Thanks

Andy

Settings wise there's only one, maybe two that are specific to AC output- AC balance and (on many inverters) AC frequency though high end kit sometimes offers a choice of waveform

AC balance... sometimes called 'clean width' biases the AC output toward either more EN (electrode negative) which heats the work or EP which provides the cleaning action (moves the oxides to the edges of the puddle). During the EP phase most of the arcs heat is put into the tungsten- too much and the tungsten will melt excessively, though it's usual for the tip to round off. Not enough EP results in a sluggish puddle, often with 'bits' in it as all the oxides aren't being moved.

Different kit behaves differently so you really need to experiment to find the range that works best- start at around 65-70% EN and run beads on some offcuts at different balance settings noting the effect on both the puddle and tungsten. A bead with black specs in it is a sign of not enough EP, black 'soot' on the weld is from sticking the filler into the arc/burying the tungsten in the pool

AC frequency has a few effects. Higher frequencies tighten the arc cone, improve focus and result in a slightly narrower, deeper weld pool. If your set has this feature i'd start with it at 60Hz (maybe 90Hz for fillets) which gives a fairly soft arc and slows things down a little which may help until you get used to the way Al behaves. Frequencies lower than 60Hz can be useful for buildup work but i usually run in the 70 - 110Hz range depending on joint type

Due to Als themal conductivity you need (initially at least) more amps than for steel despite it's lower melting point. As the part heats up less amps are needed (or faster travel if not using a pedal). Avoid playing on very small offcuts as they just magnify this effect and make life harder. Slightly longer slope out times are needed compared to steel but it's still very prone to crater defects- adding an extra dab of filler when ending a weld and keeping the arc moving in small circles during slope out will fix this

Cleanliness is important with aluminium but some people (especially on internet forums) would have you believe that it MUST be wire brushed and degreased to even stand a chance! Hydrogen is very soluble in liquid Al but not at all when solid- dirt, grease and moisture are all possible causes of porous welds. An old casting does need very thorough cleaning to get sound welds but new aluminium needs very little attention to get sound welds. As with stainless avoid using abrasives that have previously used on carbon steel. Older material with a thickened oxide layer is best cleaned with a STAINLESS steel brush or scotchbrite to remove the oxide layer before welding

Tungsten prep is slightly different. Traditionally a pure or zirconiated tungsten was used with a 'balled' tip instead of sharpened. Inverters allow the use of a sharper tungsten but leave a flat at the tip (rather than a point) and a steeper taper. The tip will round off with use.

Thanks Hotrodder
Very comprehensive!
In the manual about TIG AC-balance it says this :-

"In AC welding this section allows to adjust cleaning/penetration balance.
Penetration can be adjusted from 15% to 85%"

Click to expand...

I had it set to 50% when I last did some Ally welding???
I'am not sure if my Welder has AC Frequency, the manual only lists a frequency change on 'Fast Pulse' option
The options for Fast Pulse are :-
Base amp [a%]
Pulse Frequency [Hz]


Last time I did some Ally welding, these are the basic settings that I used :-

3 Seconds Pre-flow
6 Seconds Post Flow
50% AC Balance


Thanks

Andy

Excellent answer from Hotrodder, The only thing I might add, is to experiment with the balance and pulse settings, and make notes as to the effect the changes make to the welds, don't be afraid to take the settings to their extremes to gain an understanding of what will happen, and as said don't play about with small pieces, invest in a length of ally bar to cut up and some decent sized pieces of sheet, if you want to learn to weld you'll have to produce some scrap doing it.
Keep practicing, and post some photos of your progress.

Re Basic Settings for Aluminium

All my welder has is post gas on ac and dc but i do agree with larger pieces
to practice on

Just done a quick google for nexus 250ac/dc, the manual? agrees, you don't have adustable AC frequency (it's useful but no biggy). Pulse is different, switches between high and low amps when welding, more info in this post. Looks as though a fast pulse is only an option with DC from the manual. It's most useful on very thin material, i'm not a fan of it on aluminium personally. I'd leave it off until you get used to the way Al behaves and then you'll be in a better position to experiment and draw your own conclusions

3 secs pre flow is more than needed, just wasting gas imo. Set it to 0.5 - 1.0 sec and forget about it unless welding exotics like Ti.

Not all squarewave machines are equal (waveform on some is more 'square' than others) but i suspect 50% is giving the tungsten a hard time. Set it to 65% EN next time and run some beads. Increase it in 5% steps up to the maximium and note the effects on the puddle and finished weld, sweet spot on my kit is 68 - 74% EN depending on other parameters (AC frequency makes a difference here). Above 75% and the puddle gets sluggish. Then repeat but lowering the balance down to 50% in steps- once you get below 60% you'll probably notice no improvememt in the puddles cleanliness and fluidity but the tungsten will start to melt excessively. At 50% EN on mine the tip remains molten unless you switch to an oversize tungsten for the amperage

Finished bead should be shiney although filler alloy effects appearence a bit. This was done with 1100 filler on 3103 or 1050 parent (uncleaned, just removed from the scrap bin). Ignore the unprepped tungsten (long story, was done to illustrate a point about tungsten choice/prep on aluminium) but note the sinkage at the end of the bead due to the small coupon- ran out of pedal adjustment



Time to go and get a liquid dinner . Merry xmas all!

Thanks Hotrodder
Very nice Weld you have there!
I would be very happy if I could get slightly close to that
What approx. size aluminium bar / Plate would you suggest I use for practice purposes?

Andy

3 x 9" coupons (resulting in 6 x 9" for a finished butt weld) would be a good size initially imo. Another way would be to use with slightly narrower strips but tack a bunch together to give 2 larger coupons, each with multiple joints- alternate between them as a means of controlling temperature

hi hotrodder, thats a very nice bead. i have done a bit of practice on sheet same as you had there and end up with a crack all the way down the weld. did'nt use filler wire though. will cut and paste out what you said there and print it up and try again. when you talk about balance, is that the + and the - on the square wave. have a ac/dc transformer. kempotig 250 with no manual.

Yep, balance is the + and - ratio on the AC waveform. Transformer based machines usually need a bit more EP than inverters as the squarewave isn't as 'square' as inverters. Regardless of how the dial is labelled they're generally limited to around 69 - 70% EN, most i've used usually have a sweet spot around 5 - 7 on a '1 - 10' scale but as above, experiment

Some aluminium alloys cannot be welded without filler- generally any of the heat treatable flavours will almost certainly crack as the weld solidifies. It's generally best to always use filler for Al welds, autogenous welds only really work for closed outside corners even on the softer alloys.

thanks for getting back. i will have to pick up some filler wire next time i go to my suppliers. i have 1mm mig wire, not sure what spec, could i use it just for pig iron as they say. my machine seems to have three settings, +, -, square wave. i use + for mild, stainless, perfect, no problems. not sure wether to use the - or square for alu, will have to get a picture of the front panel up on this tread. thanks again

Now i'm confused! Mild/stainless are welded with DC but the torch is always negative (DCEN). If the torch is connected to the + the tungsten will melt as around 2/3 of the arcs heat occurs at the +ve. Aluminium/magnesium are welded with AC so the polarity is constantly changing. AC is a sinusoidal wave (as mains leccy), squarewave is very similar to sine, just more efficient

AC balance (some basic/early kit has this fixed at 50%) manipulates the sine or squarewave, biasing it either way around 50%

Yep Al mig wire will work, small diameter will make it hard work though. There's 3 common alloys used- 1100 filler (for 1xxx and 3xxx series alloys where colour match / ductility are important) 4043 (general purpose, 6xxx series alloys, almost always the right choice for castings) and 5356 (5xxx 6xxx and 7xxx series alloys). The MIG wire is almost certainly 4043 or 5356

hi, sorry, meant to say i weld mild and stainless in the - setting, i think the + and - settings are DC and the square is the AC setting. then there is the AC balance, with its own plus or minus setting. there is also the whole slope in and out set up which i dont think works, not 100% sure though. the machine produces a crystal clear ark, beautiful really, i think if i get some filler wire it will make a big difference to the alu welds. machine is a transformer type. also have a pedal which i hav'nt used yet, although i think i will give it a go.

The slope controls just smoothly ramp the amperage up/down over the no. of secs selected to prevent blowing away an edge when arcing up and craters when shutting off the arc. For example if you select 3secs slope down, when you switch the arc off it'll stay on for 3secs smoothly winding down to whatever the crater current is set at- sometimes set as an amperage, sometimes as a % of main current. Initial amperage and slope up are just the opposite. Both are switched off when 'remote' is selected (foot pedal etc) as you control slope manually

cheers for that, now that you mention it i think the slope fuction does work. i actualy bought the machine to tig up bright mild steel. my telwin 160 amp scratch inverter is great for stainless but little holes appear when welding mild, although then again, i used stainless filler for both metals. the kemppi transformer is old but is a major step up as far as weld qaulity goes. have pulse mig'd the alu no problem, its the set up time though, could be two hours on a bad day, you can set a tig up in 30 seconds (when you know whats what of course) which makes sense when you want to do 20mm of weld.

hi hotrodder, heres the front panel, the knob for down slope got knocked off a few months ago, will fix it soon no point letting these thing go, i think the AC balance is a the bottom in the middle. do you have any idea what the rectangle with the arrow going through the corner is, i think its the pedal but not sure.

Yep, AC balance is bottom middle and bottom left is the connection for a remote (pedal etc). Happy New year all

Does any one have a manual or know what every function does one these Kempotig 250 AC/DCs? I am from America and have recently aquired one and Kemppi is quite hard to contact. I can find no real info on these welders. How old are these machines? Are they any good compared to American welders? Any help would be greatly appreciated especially what controls and knobs on the welder control.

I take it then you view American welders as the gold standard. How very American! Sorry, that's not meant to be rude; I just found it amusing.

Your question. I've contacted Kemppi before now and they're prepared to sell manuals for obsolete products. I don't know how easy they'd be to contact from the US though. You could also try Westermans who are can also provide manuals for most things but may charge. Or, if your welder is the same as the one as in the pic above (or equally if you have a pic you could post), it wouldn't be too hard to run you through the controls.

Archie said:

I take it then you view American welders as the gold standard. How very American! Sorry, that's not meant to be rude; I just found it amusing.

Your question. I've contacted Kemppi before now and they're prepared to sell manuals for obsolete products. I don't know how easy they'd be to contact from the US though. You could also try Westermans who are can also provide manuals for most things but may charge. Or, if your welder is the same as the one as in the pic above, it wouldn't be too hard to run you through the controls.

Click to expand...

Archie I appreciate the info. Kemppi was quite quick in there response to my first e-mail but have yet returned my second e-mail. I just wonder how this machine got here to this side of the pond? Kemppi shows no sales or service providers on there world map in America.

As to the statement I made about American welders I did not mean to sound as a typical American but please understand we pretty much only have access to Miller and Lincoln machines. Esab has went by the way side as well as other good brands such as Hobart, Linde, Airco A.O Smith, and Pow-con
All we have now is cheap imported junk from China. I was hoping yu would say that this Kemppi will out weld any machines available in America. It stick welds fine but it is no Lincoln SA-200. It does Tig weld carbon steel very well and probably better once I figure out all the controls fully.

I wish America would stop importing junk and start importing all these machines I see on good websites like this one. The Kemppi's, Fronius, Cemont, Nexus, and Lorch's will never see full use in America because we are
addicted to the cheap stuff from China. I will tell you right now I have no
xpierience with these machine from other countries but would love to try them. On a side not what do you fellows on that side of the pond do for engine driven welders? Are Lincoln or Miller available there?