Failed weld on aluminum tube. Why?

I would try rather heavily V'ing out the lower tube - at least half-way thru the wall thickness, maybe 3/4 of the way. First, it guarantees that you have clean metal. Second, it removes some of the thermal mass from the joint. And third (most important), you can actually penetrate all the way thru rather than just laying a bead on top of the joint.
 
erikmannie said:
Are you using 4043 filler material?
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Yes, 4043 rod.

jmkasunich said:
I would try rather heavily V'ing out the lower tube - at least half-way thru the wall thickness, maybe 3/4 of the way. First, it guarantees that you have clean metal. Second, it removes some of the thermal mass from the joint. And third (most important), you can actually penetrate all the way thru rather than just laying a bead on top of the joint.
Click to expand...

Thanks, JMK. I'll try that.

I doubt my problem is about clean material material or rod. If it was that, my test weld would have been funky, too.
I don't think I've ever cleaned a rod with scotch bright. I do regularly wipe them with acetone.
I'm pretty meticulous about material cleanliness and tungsten condition.

I'd bet it has to do with the corner of the tube being a heat sink, and probably my arc was too long and wandered.

Serendipity, Miller sent an email with a link to 10 TIG welding tips right after I posted this thread.
One of them was about too long an arc and how that makes it wander. I remember it doing that.
 
Arc length and torch angle together with unsteady hands and not enough amperage are the #1 culprit for not being able to fuse aluminum butt/corner joints from what I've seen on various forums throughout the years, and trial and error on my part. You have good gas coverage, just make sure you dial in 1.5A per 0.001" of thickness (about 180A for 1/8" thick aluminum), because that is what you need at the beginning of the weld to get the puddle started; then you need to back off the amperage via the footpedal as the aluminum starts to quickly wick heat away into the rest of the part. Also filler wire size plays an important role, it should not be overly large especially if you are scared to pour on the power at the beginning. 1/16" filler rod diameter, but most importantly, keep your arc tight and straight (no more than about 3mm or so, and keep the tungsten within 10-15° of the vertical/normal/perpendicular to the joint/surface), and avoid gaps! Gaps make everything 10x more difficult. With parts butted up together properly, you can easily pour on the power and fuse the joint almost instantly so long as you're not wearing your skirt and are wearing your big boy pants when you mash the footpedal down. That first pic in post #17 could have been easily done if you would have just poured down the gigawatts. Don't be scared, but in order to not be scared, keep practicing on scrap. You need to push and "mentally power through" that initial scared-ness of using a lot of amperage by learning the timing. Learn to pour the power quickly, but you also have to react fast because you need to learn when to add filler (at 90° to the tungsten I might add, to the leading edge of the puddle, and quickly! ), and when to move right along and simultaneously determine when and how fast to ease up off the footpedal. It's a large balancing act with 5-6 different variables that you have to learn how to control with precision.

As much as you described the situation, you never actually told us anything about the machine, it's settings, your technique, torch setup, tungsten stickout, arc length, or anything else that really matters. Hopefully all those things are 100% in order, that way you can simply focus on technique which will come with practice. I know I get out of practice quickly if I don't have any projects on the horizon, and I have to get scrap the dial my brain in all over again.
 
I'm with Brino, AC balance and consider the area your heating up. The bottom piece has more mass...whereas the top piece you just have the wall of itself to heat up. Keep you cone focused more on the area that is going to take more heat to get flowing. Sometimes dropping down you wire size on you rod could help you. Using your pedal, you may have to watch and react. If you AC balance isn't correct (normally 70/30 at least to start) its difficult to bust through that oxidized layer (which is pretty much always on aluminum)
Looking at you welds, it looks like you have enough heat to get the piece puddling, but adding that wire sucks it out. I see a lot of technique issues. Just because you rock at steel doesn't mean it will translate to steel. Make yourself a bunch of coupons, learn cause and effect. With what your doing, you may want to practice welding a ticker piece to a thinner piece. Being you puddle want to flow towards gravity, it's complicating what your trying to do, if that is how it's positioned while your welding... I know that all makes for a aggravating situation...that add all kind of issues to welding
 
Thanks for the tips, General Zod.
My general method is to use the settings on the inside of the lid and tweak on practice pieces of the same thickness until it feels right.

I honestly couldn't tell you what the power settings were, It was almost a year ago on that project.
It's a good bet they were about what the chart on the door recommended.
I usually keep my foot in the peddle until I see the sluminum shine and puddle. Then back off start feeding rod and try to move fast.
I was probably using 1/16" rod and the tungsten was just slightly proud of the gas nozzle. At little further out when doing inside corners.

TIG welding is hard. Probably one of the hardest things I've tried to learn. I probably have no chance of getting real good because I just don't do it every day, and I think that's what it would take. I practice a long time before I start every project to remind myself of technique and acquaintance muscle memory. I've don't may jobs that were good enough (not too ugly) and some that turned out very pretty.
 
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Many important things have been brought up in this discussion but not put as I would say it so here is my $ worth. When welding different thicknesses together I try to use the thicker metal to control the puddle and the amount of heat going into the thinner metal. This is based on welding steel with a DC welder and stick rod. A novice could look at my work and tell you correctly that I am not a "welder", however I have a home-made fork lift attachment for my tractor that will lift the front of the tractor with the fork tips.

Experience is the key factor in all of this and changing one thing at a time is probably the next important.
Have a good day
Ray
 
Yeah...what @rock_breaker says! Good to hear you around the forums Ray...
TIG is hands down the most technical of all the welding styles. SO MUCH technique, torch height, angle, foot/amperage control, rod feed, diameter of rod, feed rate....some I didn’t even bother to post.
Lots of good training videos on YouTube using practice coupons. I was entirely MIG many years ago, once I became proficient in TIG, I never looked back.
 
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