Thread: MIG Welding Aluminium

Originally Posted by gazza2009au

just watching the video at 4:50 he shows a low wire speed and very high volts my chart is showing just over 50% volts and almost maxed out wire speed

wouldnt low wire speed and high volts cause burn back?

You're on the right track with your thinking about the relationship between wire speed and voltage. Extremely high voltage versus low wire feed will definitely cause burn back, but there is a bit of room to move within the acceptable range.
There are a couple of factors that come into play in addition to the two dials. One is the wire diameter, the second is the actual feed capacity of a given machine. If we take two machines with wire feed dials graduated from one to ten, but one machine's maximum setting is 20 metres per minute and the other one can only feed at 10 metres per minute, then it follows that to achieve the same result, one machine will have it's dial twice as far round as the other one. Wire diameter will have a similar effect proportional to the cross sectional area of the wire. .9mm wire has a cross sectional area of .636mm^2 and 1.2mm has 1.13mm^2 or nearly double. That means that if we take two identical machines, one loaded with .9mm and the other 1.2mm, the .9mm machine will need roughly twice the wire feed rate to equal the same volt/amp ratio. So to answer your basic question, his welder probably has a greater feed capacity or he is using larger wire.
This illustrates why learning to set a machine up is so important as charts provide at best a rudimentary guide. There are many external factors that can affect the charts accuracy. I have known a workshop where all the single phase migs would need their settings tweaked at around 4:00 PM as that was when the locals started cooking their tea and there was a sufficient voltage drop in the grid to send the machines off song, or the coal mine workshop where the single phase migs have differing settings based upon whether the mine is operating or not, (it's a 5 day a week operation). 3 phase gear seems to be affected less, probably due to it's greater power reserves I guess. The temperature of your ally can have a far bigger effect on settings than many realise too due to ally's excellent heat conductivity sucking the heat from your weld.
Tuning your mig is one of the keys to good welding. Try to listen to the sounds of the arc and watch the way it behaves in the video I linked, then play around trying to duplicate the same type of behaviour with your machine. Have a few spare contact tips handy, I fully expect you will burn up a few while you learn, which is totally normal.

this will be my last attempt at welding aluminium ive gone with TIG didnt pan out now im trying MIG if this doesnt work out im giving up on aluminium i will than try either MIG or TIG stainless steel either way i want to achieve something

karl thanks mate i didnt take it the wrong way i know my welds are next to crap but thats the whole process of learning to weld by my self and using forums like this for advice

yesterday when i was setting up the new MIG machine i removed my old regulator low and behold i found the most likely problem to my whole TIG welding aluminium contamination problem, their is a rubber seal on the regulator the part that screws into the argon tank neck and the rubber seal was pinched no doubtfully letting in oxygen to contaminate my welds

im awaiting for a phone call from the ebay dealer he is going to explain how to MIG spool gun weld the aluminium

Originally Posted by gazza2009au

this will be my last attempt at welding aluminium ive gone with TIG didnt pan out now im trying MIG if this doesnt work out im giving up on aluminium i will than try either MIG or TIG stainless steel either way i want to achieve something

karl thanks mate i didnt take it the wrong way i know my welds are next to crap but thats the whole process of learning to weld by my self and using forums like this for advice

yesterday when i was setting up the new MIG machine i removed my old regulator low and behold i found the most likely problem to my whole TIG welding aluminium contamination problem, their is a rubber seal on the regulator the part that screws into the argon tank neck and the rubber seal was pinched no doubtfully letting in oxygen to contaminate my welds

im awaiting for a phone call from the ebay dealer he is going to explain how to MIG spool gun weld the aluminium

All good then Gazza, I was referring to the welds produced by the youtube welder, not yours.
Ally is not the most forgiving material at times. If I were next to you when you were welding, I could sort your problems and get you in business, but it is very hard to do this over the net. Don't lose heart, you were on the edge of success with your TIG welds. Mig is not overly suited to the thicknesses of ally that you are attempting, making your job even harder.
Hopefully your chat with the seller will clarify a few things and you'll be on your way.

Originally Posted by Karl Robbers

Ally is not the most forgiving material at times.

Certainly agree with that one. One of the best bits of advice I had from an experienced Al TIG welder was (paraphrased) "get it hot enough to melt and then jam the filler rod in". I also worked with a couple of gun Al welders who would not use MIG on thin (sub 2mm) Al because it was too difficult and they could go just as fast with TIG. It takes practice to be able to weld it consistently well - in fact I have a mate who refuses to learn to weld Al because he maintains he hasn't the time to regularly keep his skills honed.
So... persistence.

Michael

Dead right, Michael.
One of the hardest things for many to come to terms with is the fact that ally gives very different signals as its heat increases to melting point compared to steel. That and the fact that travel speed is increased greatly compared to steel necessitating all the welders moves to become more fluid and co ordinated. Watching a good ally TIG welder in action, their fingers move feeding the wire at a speed that a rock guitarist would be envious of, particularly when the thinner sections are being welded.
This is why I always push for people to learn MIG on 5-6mm material and TIG on 3-4mm material as these are more tolerant of pauses and hiccups.
It is very hard to learn/teach online too. Pictures and videos can only tell so much and being able to offer advice in "real time" is so much easier. A lot of the Ebay gear needs a few tweaks before it perfoms properly too. Often these tweaks are such that only a more experienced eye will spot them.
My ideal progression would be to teach someone to stick weld, then steel MIG, steel TIG, then Ally TIG or MIG.
We'll get there though.

hey guys i tried the ebay sellers setting of "E-5" and kept getting burn back not to the point i was melting tips but the wire feed wasnt enough i could clearly see the wire burning back and stopping the arc, so i turned up the wire feed just a little to as pictured and ran these two lap joint welds now u might say my welds are s%*# but from the look of these two welds im doing ok i think anyway, i was using a back and forth zig zag motion welding from right to left

gas is set at about 19-20 something i forgot what the gauge said

ive ran out of aluminium to weld but ive found welding strait flat 3mm is to thin where as welding a 6mm (2x 3mm layers) lap joint that is 6mm thick works beautiful

The weld on the left in photo 24 is starting to look like we (and you )want to see. The weld in number 27 is too cold and you can see the lack of fusion on the bottom plate. I suspect that your wire speed could afford to still go up a bit as it looks to have been a very "volty" weld, but the wire brushing of the weld could also give that impression. Can you see how the first 30% of the weld from the right hasn't really wetted in to the bottom plate as well as the remainder? That is a characteristic of ally MIG welding. It takes a little bit for the parent metal to get adequate heat into it and the welding process to settle down. If you look at many ally boats the first 40 odd mm of their seams has been gone over with TIG for this reason.
These welds look like they have been wire brushed after you did them. When you get some more ally and have a bit more of a go, can you post the pics of the welds either as welded or after a wipe with a rag? The reason I ask is that we can tel a bit more from the as welded appearance, because wire brushing modifies the surface finish, removing a lot of information about the weld and how it has progressed. If you can try to do your practice runs say 100+mm long that will help too as we can see the true weld once everything has stabilised.
If you can either get some ally flat bar, say 50X6 to 100X6, (cut into 150-200mm lengths ideally), or some 5 or 6mm plate offcuts they will be your best bet to learn on. If new material, they shouldn't even need wire brushing or anything pre weld, maybe just a wipe with metho if you want. Don't be afraid to cool the plates off if they start to get hot. Remember, you will be welding on cool material in practice, not metal pre heated and this will affect your settings, giving you a false impression of where you are and also increase the chances of melt or blow through on 3mm and below.
Definitely heading in the right direction though .

thanks karl, do u think the non fused weld was because of gun angle? here are both welds without the black stuff removed

Gun angle can play a role, but in this case I don't think it is as likely as just a bit too cold. The black stuff on the surface of the completed bead suggests contamination of some sort, only minor though. Certainly not worth focusing too greatly upon.
I generally find that angles 45-60 degrees from horizontal work for ally. You want to keep your gun nice and close in to the work too to maintain a good gas coverage - ally is less forgiving than steel in this regard.
I look forward to seeing some more runs from you when you get some more material.

I typed out a bit of reply a day or so to this, but I think I forgot to press submit. Anyway the shortened version goes like this...
- I reckon Karl's advice has been spot on here and from my reading has always been given in the most positive way possible
- Gazza, I'm another guy who reckons you were just about there with your TIG welding. It's a shame you didn't see that through to get the results you were after as it is a great process for aluminium and can be very quick with a bit of practice.
- Having said that, I'm surprised that those MIG welds are looking as good as they are. When I read the first few posts here about the ebay machine I wasn't very optimistic. It seems that with just a bit of tweeking you might get some acceptable results there - so well done.
- the thought of you doing a fuel tank for the boat still terrifies me though. There's plenty of other aluminium projects out there which are less life threatening
- regarding the welds, I definitely would practice on something like 6mm before the thinner stuff. I don't think the idea of joining individual spots is a good one. Make sure you do some destructive testing and work out where the welds are failing so you can improve on both appearance as well as functionality.
Good luck with it
- Mick

success used 50x6mm 200mm lengths i tacked each end than ran a full bead around 180mm, i used the settings inside of the welder for 3.2mm aluminium and it worked great the first part of the weld was cold and splattered a bit once i got half way thru the weld the sound changed to a hiss from a zap and it welded great at that point i actually thought i was going to blow thru but could see it was getting great penetration

last post was about an easy inside corner weld this time its a outside corner weld and it was easy as

i lowered the wire speed but kept the same volts as the inside corner weld

Starting to see some good results now Gazza.
The fillet weld clearly illustrates what I was saying about the ally mig process taking a few mm to settle down, clear the oxide layer and get the heat in the material. Bigger welders and higher amperages minimise this, but never eliminate it totally.
Your outside corner joint probably isn't set up as well as it could be and its strength will be lessened due to this. You would be better served by setting it up with the inner corners of the material just touching, corner to corner. The overlap that you have in your set up means that there is far less area for the wed to penetrate and you end up with only a thin strip of weld metal holding everything together. I am guessing that you chose your set up so as to avoid blow through, but I reckon you will find that it won't be a problem for you with the correct power and travel.
I would like to see you increase your power once you get a bit more confidence, remembering the general rule of mig welding, particularly ally, that you run with the highest power that you can for a given material. You want to get in and get out quickly with ally. This actually becomes more critical on thin material if anything.
Overall, looking really positive, with a nice clean bead after you wipe the smoke off. Keep it up.

thanks karl, i'll try the different corner weld tommorrow as u suggested but what motion of the gun should i use so i dont cause blow thru?