Toysrme

These pipes are not thick enough to constitute beveling. For that matter they don't constitute two-passing.
For that thin ---- Hell I only use 80 amps when Im doing that stuff pulsed 1 pass. That's more like 60amps for me.
Try to keep your tig pipe welds running atleast somewhat uphill. It'll make it alot easier on you.

Get some pure tungsten and ball it. The newer inverter welders do great well with alloy tungsten electrodes, but the older transformer welders do not. You have an old transformer welder.


What t_cel_t told you. Don't overheat the aluminum so much while you're welding it, and use only as much filler as you need. Your longitudinal cracking is from how fast the aluminum cools back down when you heat it up. It simply pulls the weld apart as it cools. Not helping you is your inconsistant use of filler. Remember that anytime you apply filler to a weld you're basically throwing ice into boiling water. Even tho the metal is still i a puddle, youve chilled it rapidly compaired to what is was before dipping.



AFA that stainless pipe you bought, keep good gas coverage and don't overheat it. Two pass it if you want.

gon3r

i would backpurge the stainless. if it is 16 gauge, one pass 45 amps max. just make sure everthing is clean and you should be fine. don't use abrasives like sand paper or flap wheels or grinding wheels to clean your material (alum and ss) if you can avoid it. doesn't matter as much with mild steel... if you do use abrasives on the base metal, you are putting particles of the abrasive used into the base metal which can cause contamination.

turbob16hatch

i bevel everything i weld, it gives me a nice channel to add filler to when welding it also keeps me going straight. i use 40-50 amps and .045 filler when doing 16 guage. i only one pass it as that is all that is needed and i can get full penitration just fine.

Toysrme

I don't bevel tig work under 3/16" thick in the real world.
For manifolds / exhaust pieces I don't bevel or two pass anything under schedule-40.
Alot of guys two-pass everything. I find it a waste of my time and consumeables at home.
If it's a thick piece and I need the penitration on a manifold or exhaust I simply forgo any beveling and use the correct size root gap.

cjernigan

When I say I beveled the pipe I mean I spun it against the grinding wheel quick and ended up with a bevel through half the thickness of the pipe which is basically nothing. I'll try it with no bevel for the heck of it. I'll also leave the aluminized coating alone and I'll stay away from abrasives.

I'll try the pure tungsten I bought for my next aluminum welding practice as well as all the other tips everyone has been offering up.

As for backpurging the stainless, that is going to be a bit difficult for me. The school doesn't have any of the hoses setup for anything close to a decent back purge setup. For my first downpipe ever and my first time welding stainless I think I'm going to pass on the backpurging just because it will take too much time to round up the ---- to backpurge my mediocre attempts. For the next project I will have a setup for backpurging. Atleast a hose with a valve on it, maybe some endcaps or ductape.

Someday i'll try to pulse when I have some aluminum skills honed.

Is ER70 a good rod to use on this aluminized ----? Should i use thicker than 1/16 filler rod on the aluminized and stainless tubing? I think its all .065 wall.

turbob16hatch

you eather come from a background of if it is stuck together it is welded, or some kind of industrial work where looks doesn't come into play. i for one like to make my welds look good as well as be just as strong as needed for the aplication. trying to gap peices makes no sense at all. just take the 2 sec with a flap disk and bevel the peice.

mandrel-bends

The aluminized tube can be fusion welded with proper fitup. Unless there is a gap, you won't need filler. 65-70 amps. Verify your penetration by welding up a few test samples then cutting them apart and inspecting the seams. The biggest mistake people make welding tube is they weld in the same direction on opposing sides. You want to weld clockwise on one side, then counterclockwise on the other (always opposing). This cancels out the directional warp.

Engloid

An exhaust shop wouldn't grind off the aluminized coating. However, they only want it to be fast to make, and last a year or whatever warranty they give you....and they MIG it. For what you're doing, I'd definitely do a better job cleaning off the coating than you did. I'd clean it off the inside also, or it will still get in the weld. ASME requires that you clean to bare metal 1" back from the weld. I know you don't need that much, but the reason they do it is because any contaminants closer to that can pose a risk by burning and the smoke contaminating the weld. If it were me welding that, I'd clean back about 3/4" with a flapper disk and use a rotary file or flapperwheel on the inside.

I'm a little stumped on your statement that you have never welded aluminum. The one picture you posted of the crack looks like aluminum, but I thought you only had aluminIZED and stainless tube. If it's aluminum, you will need to weld on AC. For aluminized, consider it just mild steel...because it is after you clean off the coating.

As for the reason for the crack...the comment about heat causing cracking is somewhat correct. A crack at a start like this can indicate that you fired up and ran with it without letting some heat soak in a little bit...which would cause it to crack as the heat soaked out of it too quickly, but it looks like it was plenty warm enough. That leads me to think that you got it too hot, and didn't add enough filler, which reduces the magnesium content. It then loses its ductility and can't handle the normal stresses of cooling.

Bevel: I wouldn't bevel it at all, only what it took to debur it. Consider a file if the belt sander takes it off too fast.

cjernigan

I was practicing the aluminized tubing and figured what the hell lets attempt aluminum for the hell of it. No rime or reason to it, just wanted to try it.
Sounds like I need to try a few different things to get it all figured out. Thanks for the tips, much appreciated.