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Old 09-17-2008, 07:18 PM
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TIG Welding Aluminum

Hey guys, I wasnt sure where to post this but I hope this is the right place. Ive been welding for a bout 4 years now, one of those years was with a TIG (Lincoln Electric 225), but all that experience was on steel. So recently I decided to try to stick some aluminum together....

Well lets just say it didnt go as planned, and I have yet to successfully weld 2 pieces together. Like learning with steel, I began to just run some beads on a flat piece of metal, and after some learning I was able to make a nice long stacked bead with good penetration. When I tried putting 2 together though all I did was melt the corners away, now I cleaned it really well, and I have a high amperage and I preheated it a bit, but can anybody tell me anything else I should be doing to try and get it to stick?

Thanks Alot!
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Old 09-17-2008, 07:32 PM
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How thick aluminum and how much heat are you using, also are you using pure tungston not 2%?
It sounds like you have too much heat if you are melting the corners away, I try to start 1/2" or so from the corner and work to it. Also welding aluminum is different than steel on steel you have one continus bead and you use the tortch to push the filler where you want it, on aluminum you have a bunch of spot welds that overlap and you or at least I split the difference of the two pieces with the heat and add the filler to the middle.
Are you using the pedal? I get it hot with about 1/2 pedal then as I am adding my filler step into it to get the heat and filler all at once.

The last thing is when you get the hang of it you will just all of a sudden in the middle of a bead come to you.

Hope thid helps, Mike
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Old 09-17-2008, 07:32 PM
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What kind of rig are you using?
How are you cleaning the metal before you weld it?

It sounds like you just don't have your base metals clean enough. I use a SS wire brush, mark it so you only use it on aluminum and brush the base metal 3/4 of an inch back from where you plan on welding.

The oxidation on aluminum melts at a higher temp then the clean aluminum so the inside starts to melt first then when the oxidized metal melts it just collapses.

HTH
Jake
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Old 09-17-2008, 07:53 PM
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What the others said, (both those guys have it down ),
Also, you can clean your part with some acetone in addition to the wire brush. Acetone will remove any traces of the oxidation that you can't see. On even thin material make sure your edges are slightly beveled, butted up tight and while you are learning, use a steel or brass backing plate to help control burn through. On anything thinner than 1/4" you don't need to preheat with a torch if your TIG is big enough. If you do preheat with a torch, dont preheat the edge where you will weld.

Your settings on AC should be about 150% higher than the settings you would use for steel of the same thickness. If you machine has an AC bias switch, use the max penetration setting. (Max clean will melt your electrode faster and cover it with all of the junk that is lifted out of the puddle. You need to use a bigger electrode for the max clean setting)

Get the aluminum hot, until it just begins to get shiny, then back off the pedal some and just keep the surface shiny, until you dip your rod, then give it a bit more pedal until your bead flows out...(basically what Mike H said above)...then move on, when you flow out your drop, back up a little into the previous bead to make a smooth bead.


If you see black spots and little bubbles on the surface of your basemetal while welding, then your aluminum was not clean enough...( I get to weld up all kinds of parts that have absorbed a ton of road grime, oil, etc and see it all the time )


Clean your rod with a scotchbrite pad and some acetone before you weld, dirty rod makes it hard to weld Al also.


Later, mikey
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Old 09-17-2008, 07:57 PM
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aluminum welding

My old neighbor builds circle track race cars. He says some of the glue used in new types of sandpaper can contaminate the "clean" area ...if he uses any sand[paper he followes with an acetone wash . I have a tig but always had him do my critical stuff
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Old 09-17-2008, 08:12 PM
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All good advice above.

You're using 100% argon, right? Is your filler rod clean also?
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Old 09-18-2008, 12:28 PM
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Ok, so #1 Thanks everybody for the advice! I'm still processing it, and I have yet to put it into use, but I definitely will. Now to answer some of the questions to see what I'm doing wrong.

So I'm making a corner joint and I have the edges cut at 45's and they fit together tightly. I usually have my heat at 160 amps, because I'm welding on 1/8 inch thick pieces. I have 100% argon, but I believe my tungsten is 2% ceriated, should it be pure?

I did use a stainless steel wired brush, and I bought it specifically for the aluminum, but I used brake cleaner, because I read that was a good thing to use (although I have to admit, every time I struck an arc all I could smell was brake cleaner and my nose and throat started to hurt...) so I should be using acetone. I cleaned my filler rod as well with a 3M Scotchbrite pad. For the max clean setting I can put in a 3/32 electrode and that will work?

So Mikey you say to start about 1/2 inch away from the corner of the weld (to push the heat towards the weld?) and then I make a few spot welds and fill in the middle? I am a bit confused as to exactly what I do if you could be so kind as to clarify for me I would appreciate it.

Thanks alot to everybody for their help!
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Old 09-18-2008, 08:15 PM
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I use 3/32 or 1/8 pure tungston when welding aluminum and you don't sharpen it let it ball up after you start welding.

Yes on the 1/2" from the corner. I do not start on the corner because of the lack of material to take the heat and when you are learning it only frustrates you.

I use an aluminum wheel spray cleaner to clean the material (you should be able to get it at your welding supply) and rinse it with water after spraying it.

I try to use a bit more power than I think I will need and use the foot control to vary my heat, I do like PR Mike said and get the material shiny then start adding the filler step into the heat dip then back off the heat and move to the next puddle.

Also like PR Mike said if it "peppers up" that is trash comming to the surface so keep an eye out for that, the second thing to look for is if your welds look shiny when you are done you have too much heat back off a little.

Have fun and like I said before you will all of a sudden get the hang of it in the middle of a bead but it may take a few miles of beads to get there.

Have fun, Mike
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Old 09-18-2008, 08:27 PM
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A little trick I use, (for better or worse) to 'ball' the tungsten before you weld is to switch to DC and strike and arc on a scrap piece and watch it form a ball. Let the post flow work until the tungsten cools. Don't forget to switch back to AC.
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Old 09-18-2008, 08:59 PM
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Quote:
Originally Posted by hallamwillis
So I'm making a corner joint and I have the edges cut at 45's and they fit together tightly.
I usually cut that type of joint with square corners, then butt the inside corner of the plate together.

This will leave you a nice joint that you can fill the void left by the square cut corners with filler rod. It takes less heat, and when you get your rod feeding technique down, it makes a nice rounded fillet weld on the outside corner.
Aluminum does not seem to want to fuse together as well on an outside corner as a similar steel joint.
I do fit alot of steel joints in thinner material like that, because they will fuse together with a nice bead that penetrates to the inside of the corner, but I could never get an outside corner in Al to flow that way without burning through...

I think it is because Al likes to have the arc directed upon the surface that filler rod will be deposited on, and it does not like to transfer heat to the adjoining part, like you can when welding a steel joint . I'm guessing the heat conductivity through the part is so great, it won't radiate into a part that is next to it well enough to fuse that deep..Try buttwelding 2 pieces of 1/4" plate together without beveling the joint and you will see what I'm talking about..

Maybe if someone had taught me how to weld, instead of me doing it by trial and error and cutting a and trying to break a bunch of practice welds apart, I'd have learned it differently, but what works for me may not work for you.


My first TIG job at the shop was welding up mitered corners in some 1/8" extruded aluminum angle for a local clean room factory. I took the job on without realizing that you needed AC to weld AL properly..

At the time I only had a DC machine, with no foot pedal control, and no Hi freq ....So I read in an old welding book that you could DC TIG with Helium, (hence the term "heli-arc"), and I scratch started my welds like a stick welder...


I practiced on a bunch of scrap until I got my technique and joint beveling procedure down, then sent off 6 samples for the company to X ray and inspect...They passed , and I was given the go ahead to do the job...I made 400 pieces for those guys...They said that they would never had believed that you could successfully DC weld that thin of aluminum, had they not seen it.

Lots of ways to skin a cat.

Like Mike H said, all of a sudden it will come to you, then you will find that you will much rather weld Al than steel.


BTW, the tungsten end balling method that Mike H mentioned was shown to me as well, so I know it is an accepted practice. The guy who showed me that is certified in all types of welding, and worked for NASA Ames and Lockheed, so I know he would not have done it if it was a bad thing.


Later, mikey
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Old 09-18-2008, 09:06 PM
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Awseome, thanks for the clarification Mike, and for the tips mikey! I am looking forward to giving all this a try tommorow! I will let you guys know how it went.

Thanks again for all the help!

Hal
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Old 09-24-2008, 01:03 PM
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Ok so...

I got some pure tungsten (3/32), I am using pure argon gas, I have my welder set to auto on the balance control, I have it pulsing around 20 hertz, I have it at 180 amps, my flow rate is 15 cfm, and I cleaned the metal with a wire brush and some acetone, followed up by a scrub with a scouring pad and a wipe down with a clean cloth.

BUT when I go to weld all that happens is I get a weird colored dusty looking material on top, the tungsten gets all blacked up and it wont ball... Whats up with that? It's like Im not getting gas or something, but I know I am because I can hear it coming out when I hold the torch close to my ear and press on the pedal...

Any ideas?
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Old 09-24-2008, 01:07 PM
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Gas halo isn't big enough. Try a bigger gas cup and about 20 cfh argon. Also, you should be balling up your tip on a peice of steel or brass.

Mikey
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Old 09-24-2008, 03:56 PM
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As for your tungsten turning black - that is probably because you do not have enough post weld flow. Your machine should be set so that it continues to flow argon for around 7-10 seconds after you stop welding. Otherwise - oxygen will reach your tungsten while it is still hot enough to start oxidizing.

You did switch to pure tungsten (green band) right? Some folks use ceriated tungsten sharpened to a point but only with a squarewave machine.
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Old 09-24-2008, 11:13 PM
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Well I do have pure tungsten, but my machine is square wave, would it be easier to use ceriated with a point?
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