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Discussion Starter · #1 ·
While on the subject of tig welding...

What kind of tips do you guys have for consistent weld quality on aluminum?

I've played around with a a bit and have never produced satisfactory results. most of the time I can get one piece or the other to start to pool, but by the time the other piece is ready to go I've melted the first side into a puddle of mush! :roll:

Maybe I should pre-heat in a different manner or something? I know cleaning is supposed to be very important, and I've spent a fair amount of time cleaning the pieces (what's the best method? I was using fine sand paper first, then paint thinner to wash it clean, then a towel to make sure everything is dry), but it didn't seem to help the results.

I've mostly been using 4043 filler rod, which I think is supposed to be general purpose. Anytime I do manage to stick metal together the weld is so porous it will break with a light blow from a hammer.

I wish I could spend some time watching a pro do it to see where I'm making my mistakes.. I was watching American Hotrod a few days ago, Boyd has some pretty sweet equipment in his shop..... wish I could CNC my own all aluminum hot rod :eek:
 

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Paul just got a really nice Miller Squarewave machine. He claims once the machine is set up properly, anybody can step in and do it. He did mention that you must keep things very clean. What type of machine do you have Marc?I'm the worlds worst welder so I'm not going to give any advice other than what I've been told :wink: I use the mig for tacking and then bring it to Paul :oops:

Aaron
 

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Discussion Starter · #3 ·
Hi Aaron,

I use a Lincoln squarewave tig 175. It used to be an air cooled unit that I upgraded to water cooled after I started melting torches :roll:

It's a really nice machine, I just feel like I must be doing something wrong when it comes to aluminum.
 

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Welding is tough no doubt. If I hear any good tips I'll pass them along.

Aaron
 

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Hey Marc.
You're right tig'ing aluminum can be tough especially at first. I'll pass on some of the tips that have worked best for me. I have a miller square wave with balance control and an air cooled torch (hoping to upgrade to liquid soon.) First, you're right the metal must be absolutely clean. Sandpaper will likely leave oxides or other contaminants embedded in the metal which may do more harm than good. Instead get a good selection of stainless steel scratch brushes and use them for aluminum only. Second, depending on which paint thinner you're using you may be leaving a thin film of petroleum on the surface which will smoke up the weld and make it hard to get the two puddles to dance together. Instead try acetone. If you're using a square wave machine you may want to try ceriated tungstens a try instead of pure and sharpen them rather than balling them. Square wave machines, especially those with some balance control, do a much better job of heating the metal rather than the tungsten. Ceriated (or lanthanated) tungstens will resist balling more than pure and a nicely pointed tungsten will give you much better arc control Ceriated also also has the advantage of not being radioactive like thoriated and is thus safer to handle. As far as technique is concerned this can be a tough one. I find that cradling the head of the torch in my hand rather than the handle gives me better control. You want to have the tip pretty close to localize the heat and focus the arc. I usually start on one piece and gradually mash the pedal until I get a puddle then move to the other side. Once the second side starts to go liquid, I move the torch back and forth a bit to liquify both parent materials and eventually they'll dance. Sometimes a momentary burst of heat will get the two to meet. Amperage control is also very important. I always like to set the machine to %10 or %20 higher than the goal heat and modulate the pedal. Doing so will allow you that small burst of heat you sometimes need to get two puddles to flow. It will also get you used to constant control of the pedal. Novice welders often dial the machine to the setting they see in the book for the material they're using and floor it. Pedal modulation is really important and is as much part of the art as torch control. You will find that as you move along a seem you will need to carefully cut back the heat in order to keep a uniform bead, otherwise as the parent materials heat up, the bead will widen and eventually burn through. Proper gas flow is very imprtant as well 15 or 20 cfm of argon is a good place to start, but a few extra cfm won't hurt, especially if you're welding at higher heat. A gas lens may also help as it will allow the gas to shield a wider section around the bead. For some reason gas lenses almost always make prettier welds. Finally, what alloy are you using? 4 and six series alloys will weld pretty easily, however 7075 and 2024 don't like being welded. They can be joined, but will often crack immediatly affter welding, as they cool. I hope some of this helps. I am by no means an expert and am still mastering the are myself. This is just the most helpful information I've found in a lot of reading and a lot of trial and error.

Dave
 

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Discussion Starter · #6 ·
Dave,

Thanks for the excellent information. The tough part is that I'm often not certain what type of aluminum I'm dealing with. What's the easiest way to tell on an unknown piece of metal, and what steps can you take to accomodate?

I've never heard of ceriated tungsten (thoriated, for sure). I'll look around.

Strange that you recommend sharpening the tip, just about every book I read says to ball the tip first. I also find the tip balls up naturally especially at high amperage (maybe I need larger tungsten if it starts to do this unexpectedly?).

I'll practice some more with some of your suggestions when I get a chance.

On converting to water cooled (or for any tig supplies) try http://welding-direct.com. I was able to get all of my supplies to do the conversion for around $500 IIRC.

Here's a pic of my converted setup:

 

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Marc, thats cute...DId you paint your car to match your welder, or you welder to match your car? :wink: Hehe...Yea thats the machine i Have. It works pretty well...It could use the water. but IIRC 500 bucks is huge. I find that I have to turn that machine all the way up to 175 if the alum is thick at all. Things get hot FAST, so usually I am limited to about 3 inches at a time. I agree with everthing said. Pick up some Ceriated tips.. If the tips are curlin up, go to a bigger Tung. I especially agree with the no sandpaper. THat gave me hell for weeks when i first got it.

HTH.

Hank
 

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Marc,
Identifying alloys is a tough one and I haven't yet found a solid solution. It's a pretty safe bet that most of the dimensional, unmarked pieces that you can readily obtain such as tubing, strips, bar are 6061, which is a fairly strong, formable, weldable alloy. 7075 on the other hand is most often used in machined fittings in cases where high strenth is required. Cast alloys are a shot in the dark as far as alloy and purity is concerned, although in my experience most automotive castings such as heads and intake manifolds take readily to welding. The best advice I could give here is to practice on a known alloy. Go to your local metal supplier, or Home Depot, or McMaster Carr and pick up some 1/8" 6061 strips or some plate and practice fillet welds first (where two pieces overlap). Once you've mastered some fillet welds move onto but welds and eventually work your way down in thickness. Welding a known alloy should give you a feel as to how the puddle should perform so that when you come across something that is non-weldable you can identify the different behavior. I recently experienced this while fabricating an end tank to replace a broken plastic one. I had made the tank out ot 6061 and wanted to include a bleader so I ordered some 1/8 npt aluminum half couplers and square plugs from McMaster Carr. Even though the material on the coupling was at least 3 times as thick as the sheet I fabbed the tank from, the coupling would simply fall apart before I could establish a puddle on the tank. Oh well, back to the drawing board.

Regarding Tungsten alloy and preparation. Pure tungsten should not be sharpened. As you stated it will naturally ball anyway. You can however skip the balling step in which you strike a DC Arc to a sacrificial scrap. Given the natural balling characteristics of pure this is just a waste of time as it will happen anyway. The switch to sharpened alternative tungstens hasn't been fully embraced by the mainstream, although Miller is starting to print this information in it's tig guides. Pure tungsten is still specified for aircraft and mil-spec welds on aluminum, but much of this may be due to the relatively slow adaptability of bureaucracy. I've had very good success with the other alloys and find that the ability to form a point gives me much greater acr focus. Thanks for the tip on the water cooler, btw. Now that I'm employed again I'll be looking around for one of these. I'm getting really frustrated with the air cooled unit. I was thinking of fabbing something up from an old radiator or condenser, a fan and a diaphragm pump, but for all that work $500 is pretty cheap.

Dave
 

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hey, do any of you have any opinions about the miller units? my dad pretty much only has millers (and loves them to death), but no tig welders. and him and i are looking to get a Syncrowave 180 SD. it's an air cooled unit,but you guys seem to not like the air cooled very much, would you recommend going water cooled fromt the start?

thanks,Derek
 

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Discussion Starter · #10 ·
ShavedQuattro said:
Marc, thats cute...DId you paint your car to match your welder, or you welder to match your car? :wink:
actually neither :D

I painted the welding cart to match the welder 8)

I find that I have to turn that machine all the way up to 175 if the alum is thick at all. Things get hot FAST, so usually I am limited to about 3 inches at a time.
yep, I was literally melting torches. I tried making my welding cart out of aluminum that I got free from a power company employee. Just as I started to get the stuff ready to weld my torch would just start to crumble in my hands.

I agree with everthing said. Pick up some Ceriated tips.. If the tips are curlin up, go to a bigger Tung. I especially agree with the no sandpaper. THat gave me hell for weeks when i first got it.
no sandpaper it is. I'll also go with plain acetone.

Dave:

my practice pieces are always two like metals usually cut off from the same piece of stock. I've got plenty of scrap to play with and I'm fairly certain it isn't any kind of speciallly hardened variant. Your comments explain why I was having trouble attempting to weld some hardware store aluminum brackets to a fuel rail I was playing with before I gave up and went with through-bolts.. I bet the bracket was hardened.

I looked up some of the data on ceriated tungsten and the general guidelines I read state:

Ceriatec Tungstenelectrodes, color coded Grey, are best suited for low amperage DC welding applications.

but as you say, it may not be something that has been widely accepted yet. I'll give it a shot, they aren't any more expensive than pure tungsten.

on the water cooler, I thought about using the auxilliary heater core I stripped from my 90q mixed with some sort of electric water pump but I decided for $500 I might as well buy something engineered for the task that would already accept the fittings and hose I would need to connect to my machine. The only other thing I had to buy was the adapter fittings and a new torch (I needed one anyway.. this was the second time I had burned through an air cooled torch... and I decided it would be the last time!).
 

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Marc,
Regarding the bracket, it was more likely just a crumby low purity alloy than a hardened 7 series variant. Here's what Miller Electric's Tig Handbook has to say about Ceriated Tungsten: "These are all-purpose electrodes that will operate successfully with AC or DC electrode negative. Compared with pure tungsten, the ceriated tungsten electrodes provide for greater arc stability. They have excellent arc starting properties at low current....The cerium electrodes work well with the Advanced Squarewave power sources and should be ground to a modified point." If all else fails, try looking around at local vo-tech schools. I took a night class on welding when I was in college and it was great. There were plenty of old salts who just hung out there and we had every kind of machine and material at our disposal. It was something like ten classes for $75, and I'm sure I burned more than that in 7018 electrodes and 1/2" coupons. Sometimes watching a pro do things is worth more than a thousand words. Good luck and keep us posted on your results.

Dave
 
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