Author Topic: Any experienced TIG alu-welders out there ?  (Read 32031 times)

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Offline octane

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Any experienced TIG alu-welders out there ?
« on: March 14, 2010, 08:28:42 AM »
...must be some on this brilliant forum.

Messed a bit with CO2 welding back some 20 years when I
was into cars. Never really mastered it.

Now I've decided to teach myself to TIG weld, mostly to do alu-welding
and boy'o'boy it's D I F F I C U L T !!
...but also very exiting to learn something new.

I have a cheapo Chinese set-up



...and I've been introduced to the basics
by a friend who's really good at this stuff,
so now I just practise and practice which of cause is the only way to learn this magic art.
Fortunately I have free access to all the alu-scrap I want,
so plenty of opportunity to burn nasty holes in all kinds of ways
.-)



..and after a few nights of hole-burning, contaminated electrodes, black smoke and learning my way around
dialing in the knobs on the machine,
I can do a decent seam ( is that the proper term in English ? )



...but I still have lots of difficulties actually welding two pieces together.
Sometimes it goes kind'a OK:



..but mostly I find it hard to achieve to get a pool ( dunno know the right term. What I mean is the spot of melted alu )
on BOTH pieces at the same time.

Any tricks, tips and advice from you experienced lot
are highly appreciated.

Thanks !


"A designer knows he has achieved perfection
not when there is nothing left to add
but when there is nothing left to take away"

Antoine de Saint-Exupery

Offline RidgeRunner

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Re: Any experienced TIG alu-welders out there ?
« Reply #1 on: March 14, 2010, 09:33:23 AM »
     Thanks for posting.  Don't mean to hi jack the thread but have been practicing with OX -ACY the last week myself and almost at the same point [time at it and practice pile not quite as great].  Having similar problem, pool forms quick and then wants to burn through even quicker.  Hopefully we can get a tip or 2, meanwhile back to practice, practice.

                              Ed

Offline Peter Jack

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Re: Any experienced TIG alu-welders out there ?
« Reply #2 on: March 14, 2010, 09:58:23 AM »
Try building the heat slowly, moving the torch around on both pieces in the area of the start and then going forward only as fast as the material wants to puddle. Patience counts!!

Cleanliness is also really important. I usually use acetone to ensure that there is no oily film on the aluminum. It also helps to use a stainless wire brush to clean the area you're going to weld. This breaks up the oxide film on the surface. Don't use this wire brush for any other purpose.

Hope this helps.

Pete

Offline Dean Los Angeles

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Re: Any experienced TIG alu-welders out there ?
« Reply #3 on: March 14, 2010, 10:24:53 AM »
The transition from welding steel to aluminum is like going from drag racing to LSR. Kinda the same, but way different.

First thing to do is turn off that fan in the picture. It blows the shielding gas off the weld. Real welders just sweat.

When you weld steel you clean off the rust first. Rust is the inevitable reaction of oxygen with the steel. It happens over time. Chemically it isn't far from the base steel.
Aluminum does the same thing. The "rust" is aluminum oxide and it forms instantly when you make a cut. It is very different from the base metal. In the crystalline form it's called Corundum and is used as an abrasive. Super hard and it is the primary cause of your difficulty.

Cleanliness of the surface as noted is critical. Any oil or junk makes it worse.

The aluminum sheds heat faster than you think. The amount of heat needed is way more than your steel calibrated head is ready to believe.

The appearance on the surface doesn't tell you enough when you are learning. Cut the weld on a band saw and see how far your weld penetration is going.

The amount of heat you put into the center of the part will blow through the edges.

Practice, practice, practice.
Well, it used to be Los Angeles . . . 50 miles north of Fresno now.
Just remember . . . It isn't life or death.
It's bigger than life or death! It's RACING.

Offline Gwillard

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Re: Any experienced TIG alu-welders out there ?
« Reply #4 on: March 14, 2010, 10:26:01 AM »
Tig, otherwise known as GTAW (gas tungsten arc welding), on aluminum can be a challenge. You should familiar with the basic setup which includes argon shield gas at a flow rate of around 15-20 cfh, a pure tungsten electrode, and AC current.
The next item is weldability of the alloy. 2XXX & 7XXX series alloys can be almost impossible to weld with any equipment you or I can afford. 3XXX, 5XXX, and 6XXX series are more easily welded, especially the 4XXX.
Cleanliness is vital. Remove all dirt, oils, corrosion, etc. Clean the area with a stainless steel wire brush that is used ONLY for aluminum to prevent cross contamination.
Depending on the capabilities of your power source and the thickness of your material, significant preheat may be needed. Aluminum has a high thermal conductivity so the heat you put into the are you are trying to weld quickly flows into the surrounding material. If the items are small enough you can put them in an oven and bring them to about 200 F.
At some point, probably sooner than later, you will experience weld solidification cracking. This is extremely common when attempting welds in 6061 without filler. Using a 4043 filler will help prevent this.
From the looks of your practice welds I would say you are coming along fine. It just takes lots and lots of practice. If you can find an experienced welder in your area to spend a couple hours with you they can save you many hours of frustration and lots of spent consumables and filler.
Check out Lincolns web site for some good info on welding aluminum.
http://www.lincolnelectric.com/knowledge/askus/weldingfaqs.asp
Will weld for beer :cheers:

Offline jww36

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Re: Any experienced TIG alu-welders out there ?
« Reply #5 on: March 14, 2010, 10:35:38 AM »
Octane;
Tig welding aluminum is difficult at first, but the key I have found is getting the material hot enough to form puddle, as you actually add/melt rod in the puddle. Try this. Concentrate on the puddle first, in other words, forget about adding rod to practice. Take a flat piece of aluminum, 1/8" to 3/16" thick, raised off the welding table a 1/2" or so. You will be amazed how much faster the puddle forms with the material off the table as the table acts like a heat sink. Once you form the puddle, move the torch in steady increments of approximately 3/16" or so. Once you've practiced concentrating on the puddle only, and you kind of have that movement down, try adding rod to puddle.
Hope this helps.
John


Offline Black Rose Racing

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Re: Any experienced TIG alu-welders out there ?
« Reply #6 on: March 14, 2010, 10:51:07 AM »
Would anyone like to add a comment concerning the shape of the tip of the electrode Steel vs. Aluminum and how to form that shape ?

Offline Gwillard

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Re: Any experienced TIG alu-welders out there ?
« Reply #7 on: March 14, 2010, 11:35:40 AM »
Would anyone like to add a comment concerning the shape of the tip of the electrode Steel vs. Aluminum and how to form that shape ?

For steel the tip should be ground to a taper, usually with a slightly truncated (blunted) end. The angle varies but generally speaking as the included angle increases the weld penetration increases and the bead width decreases so a flat ended electrode will give the deepest penetration and a needle-like point the least. I know it sounds counterintuitive, but it is in the way the electrons flow off the tungsten. Somewhere around a 45-60 degree included angle is a good starting place. Grinding should be done so the grind marks run towards the point, not perpendicular to it.
For aluminum the tungsten can should be balled by striking and arc on a piece of clean copper using DCEP current and a flat-end electrode. Increase current until the tungsten begins to melt and forms a ball no more than 1.5 times electrode diameter. I have used a piece of stainless in place of copper as well as a thick chunk of very clean aluminum. Don't forget to change back to AC after balling the tungsten. (I've never done that.  :roll:)
Will weld for beer :cheers:

Offline mkilger

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Re: Any experienced TIG alu-welders out there ?
« Reply #8 on: March 14, 2010, 12:15:47 PM »
first how thick are you trying to weld?  on my roadster the seat and the hood and other (big stuff) is 90 alu. I ball the electrode . but when I weld 50 alu I make the  electrode sharp which makes the bead smaller.  are you having a back crack at the end of the welds? (please no butt crack jokes)  at the end of your pass slowly let off the heat. now if you are making shaped body panels I weld the back side of the pass, just by flowing it together. Just a few tips from 20 years of metal shaping good luck.  www.millerwelds.com (bonneville in the search box)

Offline Seldom Seen Slim

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Re: Any experienced TIG alu-welders out there ?
« Reply #9 on: March 14, 2010, 12:18:19 PM »
As long as we're hijacking -- I'm not a welder (nor much of anything else, but that's another story).  So - my new '09 GMC pickup has factory aluminum 17" wheels.  No steel wheels are available, either OEM or aftermarket.  So if I want to mount Moon discs I either have to try the snap-in style (with which I've not had great luck - lost a few over the miles) or figure out who'll weld the steel Dzus button tabs to the aluminum wheels.

Any comments on how to get the tabs to stay put well enough that the things don't get bounced and flung off in the next 50,000 miles?

Oh, yeah -- I've tried the screw-on type, with drilled/tapped holes in the rim, and there was enough corrosion that the discs didn't stay on and the rims looked pretty crappy after only a few months.  I'd rather the tabs/Dzus style.
« Last Edit: March 14, 2010, 12:20:34 PM by Seldom Seen Slim »
Jon E. Wennerberg
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 Skandia, Michigan
 (that's way up north)
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Offline WhizzbangK.C.

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Re: Any experienced TIG alu-welders out there ?
« Reply #10 on: March 14, 2010, 12:47:01 PM »
Would anyone like to add a comment concerning the shape of the tip of the electrode Steel vs. Aluminum and how to form that shape ?

I use an import inverter setup much like the one that you have, and have found that 2% Thoriated tungsten ground the same as for steel works very well. There is something a little different between the inverters and the old copper wound welders that makes this work. I find that with pure tungsten on the inverter the tip tends to melt and erode way too fast when welding aluminum, and will contaminate the weld.

I've only been TIG welding a short time myself, and can share a few things that seemed to work for me as far as getting started.

Make sure that your using an appropriate size electrode. The diameter of the electrode should be close to the thickness of the material that your welding. Using a large electrode on thin material is a recipe for disaster in my experience.

On getting your puddle started on both pieces, I find it best to have no space between the parts I'm joining. When starting your puddle, especially on thin material (less than .100") pick a spot a little ways in from the end of the joint to begin the weld so that the corners don't melt away and fall off. (Once the weld is started you can go back and finish it to the edge.) Put as much heat into it as you can as quickly as you can while still leaving yourself a little pedal to work with to get the puddle started. Watch the area closely, you will see the "texture" start to change in the area you are heating before it actually melts, if one side melts and the other isn't really close move your torch slightly to concentrate more heat on the side that isn't melting. Once one side is molten and the other is really close, simultaneously add a dab of filler rod and mash the pedal for a second to get extra heat to melt the filler to both sides and create the weld pool. This is one of the most critical parts to me, because in order to insure good penetration you must have full contact with the pool with both pieces that you are joining, but you have to develop the feel for it to not burn through. (Does that make any sense :?) When I was starting I burned through a lot, and practiced till I was able to pretty much keep it right on the edge of burning through for full penetration. If you don't go over the edge a few times, you'll never really know exactly where it is.  :evil:

Once you have a pool started, it's a relatively easy matter to run the bead. I like to pulse the pedal, add a dab of filler, let off the pedal, then move a little and repeat. Just watch the pool carefully and add filler when the edges start to melt back. As your weld progresses the aluminum absorbs heat and it takes less amperage to continue the weld, keep an eye on this also and slowly back off on the pedal to maintain an even bead width. If you keep welding at the same amperage it took to start the bead, you will eventually blow a hole in it.

Ending the bead is another tough spot. I find it best to taper off the amps and slow my weld speed when I'm getting to the end of the weld. When I put my last spot of filler in I'll give a little extra pulse to the pedal and then let off completely and pull the torch away slowly in the direction of travel, rotating the head to keep the post flow gas on the weld as the machine ramps down. I find that this move helps to minimize pitting at the end of the bead.

Everything that was said above about cleanliness is spot on, don't get tempted to try to bypass any of it, it will not be good. In fact, if you've cleaned your metal, and have to leave it for some reason for more than an hour or so, clean it again before trying to weld, wire brush and all. Bare clean aluminum starts oxidizing instantly. I know you machine parts, just think how dull that beautiful shiny freshly machined surface looks 1/2 hour after you're done.

IMPORTANT SAFETY WARNING>
Use ONLY acetone or alcohol to clean the metal. DO NOT use brake cleaners or other shop chemicals ever, as they may have nasty reactions with heat and atmosphere and try to kill you. Make sure that whatever you use to clean is completely evaporated and the container is well away from the welding area before striking an arc so that you don't end up on fire.

The main thing is to practice, practice, practice. When you think it looks good, cut it and look inside the weld. Bend the parts you've welded and then cut them to see how they hold together, and make sure you're comfortable with it.

I always viewed welding as an evil necessity until I started TIG welding. Now it's my Zen place and something that I absolutely love to do. The total control and concentration needed to do good work drives everything else from my mind like nothing else I've ever found. It's better than recreational medication, LOL.

Another thing that I highly recommend is to get a water cooled torch if you're planning on doing a lot of aluminum. It takes a lot of amps and the torch can get very hot in the hand quickly. It really sucks having to stop in the middle of a good bead because your torch is about to melt in your hand. I bought a water cooled torch for about $150 and built my own cooler from a 5 gallon plastic bucket, a small pond pump, and some fittings from the welding supply shop for less than $100. It makes all the difference in the world and is the best thing since sliced bread in shirt pockets.  :-P

It looks like your off to a good start, and I hope some of what I've put up here helps. Like I said at the start, this is what works for me, your mileage may vary and it seems that everyone develops their own style and technique over time. Just remember to relax and enjoy it and have fun.   :cheers:
« Last Edit: March 14, 2010, 12:56:24 PM by WhizzbangK.C. »
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Offline WhizzbangK.C.

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Re: Any experienced TIG alu-welders out there ?
« Reply #11 on: March 14, 2010, 12:49:40 PM »
As long as we're hijacking -- I'm not a welder (nor much of anything else, but that's another story).  So - my new '09 GMC pickup has factory aluminum 17" wheels.  No steel wheels are available, either OEM or aftermarket.  So if I want to mount Moon discs I either have to try the snap-in style (with which I've not had great luck - lost a few over the miles) or figure out who'll weld the steel Dzus button tabs to the aluminum wheels.

Any comments on how to get the tabs to stay put well enough that the things don't get bounced and flung off in the next 50,000 miles?

Oh, yeah -- I've tried the screw-on type, with drilled/tapped holes in the rim, and there was enough corrosion that the discs didn't stay on and the rims looked pretty crappy after only a few months.  I'd rather the tabs/Dzus style.

Uhh, aluminum tabs???  :cheers:
Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of.  Douglas Adams

Offline Seldom Seen Slim

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Re: Any experienced TIG alu-welders out there ?
« Reply #12 on: March 14, 2010, 01:18:01 PM »
Nope, although a good idea.  The tabs are supplied by Moon -- and are steel.
Jon E. Wennerberg
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Offline WhizzbangK.C.

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Re: Any experienced TIG alu-welders out there ?
« Reply #13 on: March 14, 2010, 01:21:33 PM »
Nope, although a good idea.  The tabs are supplied by Moon -- and are steel.

I understand that, but it shouldn't be all that big a deal to make new ones from aluminum that would be weldable to the rims. The Dzus retainers and fasteners are easy enough to find. You'd want to make them thicker than the steel ones, so you'd need to get longer fasteners.  :cheers:
Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of.  Douglas Adams

Offline mkilger

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Re: Any experienced TIG alu-welders out there ?
« Reply #14 on: March 14, 2010, 01:52:49 PM »
slim, get the alu tabs  and I will put them on for you. make sure you dismount the tires first it will save you $ on shipping