I'm welding 48" x 48" 6061 aluminum film lighting gel frames from 1/4" x 1" bar. I'm welding with a Lincoln PT185, with a WP-26 torch, 3/32" thoriated tungsten, and 3/32" 4043 aluminum rod. My joints are all butt welds with the bar cut at a 45 degree miter and each miter beveled to a clean edge.
Because I've had trouble with the material literally dropping away, I'm backing each joint with a 18" x 18" x 5/8" piece of solid aluminum. This helps greatly to pull the heat out of the joint. It also obviously means I have to crank up the amperage to get a good weld.
When I get a chance, I'll post a picture of my welds. In the meantime, I'm concerned that I'm not getting full penetration on my "root" pass (I'm not actually doing more than one pass on this relatively thin material). When I weld the first side (all four corners) and then flip the piece over, I have not actually welded through. In other words, that knife edge where the two pieces meet to be welded is still a knife edge.
Should I be concerned about this? Please understand that this is not a critical application and these joints are not under tremendous stress. But still, in addition to my wanting my welds to look good, I also don't want them to break and come back to me for repair.
Any advice would be appreciated. Who knows? Maybe someone out there thinks I should be doing multiple passes, starting with a DC- pass and then switching to AC. I'm always open to suggestions.
THKS!
Jon
For your outside corners, bevel the edges “open” so that you get penetration below the surface, filling to the surface. You don’t need huge strength here, just something solid.if your application will tolerate welding both sides, and leaving the bead, it will be stronger.
The base metal melting away is too little heat, not too much heat. Swap to stainless backer or skip the backer altogether. Use a 1/8” tungsten, crank up your heat, balance at 68-72, frequency at 60Hz. You’ll punch those welds right it...
The base metal melting away is too little heat, not too much heat. Swap to stainless backer or skip the backer altogether. Use a 1/8” tungsten, crank up your heat, balance at 68-72, frequency at 60Hz. You’ll punch those welds right it...
cj737 - Thanks for the advice. When you say to bevel the edges "open" you mean to cut a 45 degree on them, right?
Yes - my application will certainly tolerate both sides and also leaving the bead. No problem with that.
I'll up my tungsten to 1/8" and crank the machine and put it at 68-72 as you suggest. And I'll lose the 5/8" aluminum backer. Rather than stainless, can I go with a mild steel backer? I've fabricated a 48" x 48" frame out of 2" x 2" mild steel as a basic "table" for the aluminum frames that I'm welding - just to keep every piece in the same plane and not hanging off a small table and being awkward. I'm assuming that the backer, no matter what it's made of, is designed to take the edge off the heat. I had already considered ditching the 5/8" aluminum as it requires me to really crank the heat and even then not always get the penetration I'm looking for.
Can you answer one more question: I tend to build up the heat to make sure that I'm not going to blow the aluminum away. I've read that this is not a best practice, that this is actually not part of the welding procedure, it's just heating the piece. So I take it that I should just hit that foot pedal to max right away, not be shy about it and back it off if I need to. Sound right to you?
Jon
Yes - my application will certainly tolerate both sides and also leaving the bead. No problem with that.
I'll up my tungsten to 1/8" and crank the machine and put it at 68-72 as you suggest. And I'll lose the 5/8" aluminum backer. Rather than stainless, can I go with a mild steel backer? I've fabricated a 48" x 48" frame out of 2" x 2" mild steel as a basic "table" for the aluminum frames that I'm welding - just to keep every piece in the same plane and not hanging off a small table and being awkward. I'm assuming that the backer, no matter what it's made of, is designed to take the edge off the heat. I had already considered ditching the 5/8" aluminum as it requires me to really crank the heat and even then not always get the penetration I'm looking for.
Can you answer one more question: I tend to build up the heat to make sure that I'm not going to blow the aluminum away. I've read that this is not a best practice, that this is actually not part of the welding procedure, it's just heating the piece. So I take it that I should just hit that foot pedal to max right away, not be shy about it and back it off if I need to. Sound right to you?
Jon
Right, romp the pedal and get your puddle. Then, taper off to maintain a molten puddle while you add filler.
I don’t like carbon backers on ally due to contamination of the ally. Throw a cover of ally foil over top so you can use the frame as a square for contrcuting the ally.
Yes, just knock the edge off the corners to open them to gain access deeper. A flap disc will work fine. Or use a compound miter saw.
I don’t like carbon backers on ally due to contamination of the ally. Throw a cover of ally foil over top so you can use the frame as a square for contrcuting the ally.
Yes, just knock the edge off the corners to open them to gain access deeper. A flap disc will work fine. Or use a compound miter saw.
Well, upping my tungsten to 1/8" and pumping up the AC balance to 72 already made a nice difference.
Didn't think of the contamination issue but good point. I'll throw some tin foil in there as you suggest.
Just a matter of practice now. It's tricky for me because at best my bead is only going to be 1" long before I'm off the end of the piece...
But I'm working it.
THKS for your input!
Jon
Didn't think of the contamination issue but good point. I'll throw some tin foil in there as you suggest.
Just a matter of practice now. It's tricky for me because at best my bead is only going to be 1" long before I'm off the end of the piece...
But I'm working it.
THKS for your input!
Jon