Thread: Tig Advice

Originally Posted by kelack

I don't have a foot pedal would that help cheers

Al conducts too well not to be able to control the current going in on the fly. You need a foot pedal or a thumb wheel to weld without over heating (or starting too cold).

Michael

Originally Posted by kelack

Hi all ive been learning to tig weld aluminium and starting to see some improvement on butt and edge welds, my problem is fillet or tee welds, filler wire was balling, but learnt to get the heat away when dipping rod but now my problem is the metal getting to hot and i have to go to fast, im useing a number 5 shroud is this to big or to small also i dont have a foot pedal would that help cheers

A #7 is my favourite size, you use a tad more argon but get better shielding. If your filler is balling up, then keep it lower, almost parallel to the work surface and sneak it in under the heat plume, dab the filler frequently, deliberately and accurately.
Provide some more details on what you're welding, how thick it is, amps, filler rod thickness, etc. and you'll get more help
cheers
- Mick

thanks guys and it is 3mm ali on about 50 amps which seems to do edge and butt welds ok but i have to boost the amps up on a fillet weld to get a puddle going thanks for ur help

50A seems way too low for 3mm. I'd be using 120A as a starting point.

Originally Posted by Legion

50A seems way too low for 3mm. I'd be using 120A as a starting point.

Definitely too low.
The good old rule of thumb is 1A per thou or 40A per mm for the metrically inclined.
If we consider the properties of Aluminium, we identify a metal with a tenacious oxide layer that must be removed before welding can take place, with a relatively low melting point and good thermal conductivity. Applying a bit of welding theory tells us that you will need to hit ally with a decent amount of power in order to get the heat in the weld zone and establish a puddle before it is conducted away and then you need a reasonable rate of travel to prevent overheating the parent metal and getting melt through. If you turn your power down too far, then you have insufficient grunt to establish the puddle before you heat the entire work piece up and melt the whole thing.
This is why some people like foot pedals so they can have a large burst of power to establish a puddle and then a lower power level to run the weld. Similar can be achieved with the 4T setting (I don't suggest this first up) or thumb wheels etc. They are by no means essential though. I have welded ally for twenty odd years and pretty well never use either.
If you come to weld some stainless, you will find that you will use far less power for a given thickness due to stainless steel being a poor conductor of heat, thus keeping the heat in the weld zone.
The best all round advice I can give you is to learn what the arc should look and sound like when all is working well and learn to duplicate this rather than become too caught up by amperages as they do vary between machines and even ambient temperatures can affect power levels required for a job. It's not as bad as it sounds, the pieces will fall into place.

The other factor to consider is what the metal to be welding is sitting on, especially with ally. If the work is in mid-air then the bulk of the heat from the torch will go into the work but if you have the work clamped to a metal bench then some of the heat will be conducted away from the work into the bench and you may well need to increase the starting amps.

The trick is to start with a burst of high current until you see a silvery mirror-like surface on the puddle and then start feeding the filler in and reducing the current (or increasing the travel rate) to keep the puddle under control. A lot of beginners are worried about melting the aluminium because it doesn't give you a colour indication of state change like steel does and so are timid and they use low amps but that can make things worse - as Karl said previously.

As others have said, a pedal makes it a whole lot easier but it's not mandatory.

sorry gentlemen as this is a uni mig 200 ac dc and i am lending it of a friend he has just let me know that the 50 read out on the digital display is in current and has a switch to give a read out in amps it now reads about 180 amps, is this to high also i am useing no pulse as i dont really understand the pulse set up as yet and am just trying to learn, think i really need a foot pedal to control the heat as the dial on the handle is out of my league ,im to busy trying to keep the tip out of the puddle. thanks for ur help

Holy cow! 180 amps doesn't leave much room for error, in fact I though Legion's and Karl's 120 was pretty high. Having said that, all machines are different, so you really do need do a test then adjust up or down accordingly. I don't think it's been mentioned yet, but your AC balance goes hand in hand with amperage. I tend to run quite low on the cleaning action (i.e. the electrode positive component), so most of the amps are going into weld.
A good way with aluminium without a foot pedal is to start at a high AC Balance (say 50%) and reasonably low amperage (I'd pick 90 amps for 3mm, but higher for a fillet) and get a puddle started. If, on a cold job, the puddle takes more than a couple of seconds to grow big enough to dip filler then you are running too cold and you should crank up the amps (by 10 amps), then try it again. If your weld continues to grow and get out of hand after 5 seconds (and a couple of filler dips), then you're running too hot.
Cheers
- Mick

Originally Posted by kelack

think i really need a foot pedal to control the heat

I don't do ally, but I've been playing with it a bit lately. I could not, at all, do it without a foot pedal. I'm riding mine constantly the whole way through. I know others do without. If I did that I'd want to have my trigger set up just how I wanted. I could not, at all, I reckon do it with a variable torch control. Maybe 2T or 4T switch and bump it down when I needed.

You don't need pulse with AC, really.

180A is a lot. That would turn a whole piece of 3mm into liquid for me. On the weekend I was running 200A but only to start and then quickly way down on the pedal and that was with probably 4-6mm material.

I hate ally for now. Steel welds much nicer for me, and is recoverable. I keep reading stuff that makes me scared of aluminium and if I stuff up I feel like scrapping the piece given I'm scared of going back over previous welds. But it's interesting learning.

There's no reason to fear welding ally, it is slightly more tricky in that it doesn't give the temperature feedback via colour changes that steel does but you get to be able to read the metal with practice - look for the mirror finish on the puddle which indicates that the metal is ready to weld. The key to welding aluminium is heat management, for example an large item will absorb more heat than a small thin one, a job sitting on a steel bench can take more heat input than one in free air and so forth, When welding very thin sheets you can sometimes use copper backing bars to draw some of the heat away to make control easier. Once you get your head around the amount of heat that your workpiece can absorb then it's just another weld and it's a matter of practice and more practice.

The biggest mistake with ally is to be too timid. If you try and weld using a low current to avoid melting the work you will just pour more and more heat into the work without getting the puddle to form and when and if you eventually get a puddle to form you will have saturated the whole work with heat and you will likely melt through. Far better to go in hotter, establish the puddle quickly and then wind back on the current and get welding.

Pulse is just another feature used to control heat input, it allows you to set the machine to run at a given amperage for a certain time and then at a lower amperage for a certain time, so it alternates between the 2 current settings giving the weld pool time to cool slightly before heating it up again. It's not something you use all the time and it's something you can play with once you have a bit more experience.

I tend to run too hot and fast rather than too slow. But visually my best welds are the colder ones. I tend to go hot and fast enough to wash out the puddle a bit too much, no matter how fast I feed filler. I need to do a few more kg of filler before I feel good about it.