Help with aluminum project

Ok guys...hoping I can garner some good advice here.
Recently received my PP256 for an aluminum project. I have adequate experience MIG welding carbon steel but have never held a TIG torch and never welded aluminum.
I'm able to run a decent bead on a single piece of 1/4" aluminum, nice width and healthy penetration but when I move to join two separate pieces the nice bead goes down the tubes.
Specs are as follows:

1/4" x 1-1/4" aluminum flat bar with mitered corners (as seen below)

225 Amps
CK 200 amp flex head, air cooled torch with superflex cable (figured I didn't need the handicap of learning with the bulky stock torch)Attachment 7523
2% Thoriated 3/32 tungsten sharpened to a point and 1/4" stickout
3/32 4043 filler
#7 cup
100 Htz Frequency
30% AC Balance
100% Argon - 17Lpm
Pre Flow @ about 1 Sec
Post Flow @ about 6 Sec
No Pulse and no Slope

Thanks in advance for your help.

Practice TIG welding steel for a while, first. It will really help.

17 lpm argon flow is too much, somewhere between 8 and 11 lpm should do with an 8 to 10 cup and around 200 amps.
For material that thick, I'd bevel the edges and use a 1/8" filler rod.
Practice on some scrap of the same thickness first, with the same joint prep.
Welcome to the forum.

100 Hz AC frequency is good, but I prefer to run a little lower, 60-90 Hz. It just seams like the aluminum flows better with the lower frequency.

If you will be anodizing this or going with a brushed/polished finish, you should switch to 5356 filler for a better color match with your 6061 bar stock. Also for that amperage you might want to knock the point off your tungsten. make a little flat on the end of the point and you will get a slightly fatter arc that will help to bridge two pieces. Be sure both pieces are grounded, and work the heat over both of them a little before getting to the puddle stage. Use the pedal to control your heat if things start to get too soft. Be sure to add enough filler to satisfy the puddle and to also control the heat.

Quote:

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Originally Posted by Markz

I'm able to run a decent bead on a single piece of 1/4" aluminum, nice width and healthy penetration but when I move to join two separate pieces the nice bead goes down the tubes.

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Show us a picture of the bad weld... Would give us an idea what is going wrong... BTW you need to hold the tungsten close to the metal... 1/8" or probably less... Just 2 cents from a rookie...

Update: I've noticed much improved results by moving the heat over both pieces and waiting for a puddle to join between the two before moving on.
Yes, my project requires I grind my beads off and sand to a brushed finish so I will heed the advice given and move to using 5356 and beveling my edges.
Also, I have sacrificed a couple sticks of material to simulate my real world welds and though they looked like they had adequate penetration, my destructive testing proved otherwise. Once the beads were ground and sanded I put them in a vise and with some persuasion they snapped right off. It looks as though I had adequate penetration at the start of the weld and at the end but almost nothing in between.
My other problem...when I reach the outside corner it just melts away though I think I'm letting off the pedal enough. Any thoughts?
Here's a photo of a lousy weld and a photo to illustrate what I'm trying to do. This was previously done in cold rolled steel though rust became a problem hence the move to aluminum. It's more difficult than I thought it would be.
Attachment 7531Attachment 7532

Aluminum is very heat conductive, so lots of things can change how the weld goes. For instance, those little samples will heat up much faster and get hotter than your larger pieces will. Same thing with clamping to a heavy steel table, it will sink the heat. It's very easy for AL to get too much heat and go out of control if you're not careful. Those points are a good example, they will be quite hot by the time you get there. Simple fix is to make that your start. I always like to start at the point of a mitered corner. If you can't do that without blowing away the corner, start near there and work out from the middle. In addition to the bevel, you might also want to leave a little gap. Then when you are welding, use just enough heat to cause a slight keyhole and you will know you are getting full penetration. Another option is to bevel both sides and weld two passes, one on each side. Many ways to skin that cat.

Quote:

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Originally Posted by Markz

It's more difficult than I thought it would be.

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Imagine that! :P Actually, I'm sure you're getting better with every attempt. Just keep at it. All it takes is practice, like most other skills.

your weld are wide because to many amps , thing with sheet aluminum have to have patience it doesn't melt to a puddle fast but when puddle forms back off on amps a little and feed filler rod . with lower amps should be a nice narrow bead and easier to work with

Start your weld at the outside corner and weld inward. You build up too much heat welding toward the outside corner.

Quote:

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Originally Posted by Rodsmachineshop

...sheet aluminum...

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It's 1/4" bar stock, the width looks about right for that. I don't think this sample was beveled. The next one will be.

You should bevel that for better penetration. I would weld the back side too, if access to the back side, (and also the extra time required to add this extra step) is not an issue. If you weld both sides, considering beveling the back side of the seam as well. When welding the second side, penetrate as deep as it takes to "wet out" the root of the joint, before you go about adding any filler rod. That will ensure 100% penetration.

Feather your footpedal to maintain a more constant bead width. It will take practice to get good at it. When aluminum starts going, it can go pretty quick. You can always take a break and let your work cool off. But for this width of bead, it's probably good to just weld it up in one straight shot (plus a tack weld or two.)