GTAW - Aluminum Thin Wall Tubing

By Lawrence (*****)

Date 03-24-2004 15:47

Hey Frank!

Welcome to the forum!

I don’t know of any good specific literature on exactly what your doing (maybe somebody else can help with that cause I would like some too) but do have a few tips that might be handy for you.

Here are some basics, in order of importance

Surface prep must be perfect, all oxides removed immediately before you weld, mechanical or etched, inside and out. Your root won't break down if there is a thick oxide layer or if any contaminant is present.

Fitup, the thinner the tube the tighter the fitup must be, no gaps!

Torch position. Keep the torch perpendicular to the work at all times, just a slight tilt will change the consistancy of your penetration profile. If you can fixture your part in a rotating positioner you could weld the whole thing out in the flat position in a single pass. Multiple arc strikes breed discontinuities.

Tip prep. I like 1/16 cerium and zirconium electrodes for jobs like yours. Forget the balled end and sharpen your tungsten not with a long slim taper but rather with a more radical angle with just a little blunt at the end. This will produce a more columnar arc and more directional penetration.

Balance control. If your powersource is a squarewave than I would start at about 65 to 70% dwell time on EN and see how that looks. More time on EN will provide deeper penetration and a more narrow profile, however be careful as too much EN may reduce the cleaning action required to get a nice fuse at the toes and root.

Aluminum likes to be welded hot and fast, with a manual project this can only be accomplished with some practice. If you have scrap put it to good use :)

By gonzalez002 Date 03-24-2004 19:17

Thanks for your suggestions Lawrence. We have already tried the mentioned steps and still can not seem to get root to breakdown.

Would polishing both the inside and outside to a mirror like finish help?

Any recommendations on the filler wire diameter?

We are currently using 4043 with an OD of 0.047 in. The wall thickness of the tube is 0.035 in.

Frank

By Lawrence (*****)

Date 03-24-2004 19:55

Sure, the polish might help, but I would think a mini-flapper (120 grit) ought to be sufficient to prep the inside of your tube.

It might be worth your time to take a step backward so to speak, and try to get the profile you want on some 0.035 plate. If you can get it to work there, in the flat position, the pipe really should work too. Sometimes when you stop and take a step back you can find the trouble your shooting at considerably less cost in time and material.

I like .063 filler in situations like yours because I can increase the amperage and use the mass of the wire to cool the puddle as I add it. For me it makes for faster travel speeds and a better appearence on the outside, but that is strictly a matter of operator prefrence on my part.

Penetration (root reinforcement) with thin wall gtaw will be greater than with stainless or mild steel, thats just its nature so don't be afraid to try a bit more heat.

By TRC

Date 03-26-2004 08:53

Hey Frank,you might want to try 4047 filler-1/16". It has a lower melting temp.

By 357max

Date 03-25-2004 14:45

I have had good success with all the procedures posted so far with the following additions, use a gas lens collet body and nozzle, a separate and dedicated (use a Tee fitting on gas cylinder with two flowmeters)flow meter & hose providing 1 to 3 cfh purge flow on the inside and using 0.030-35" (the wall thickness) diameter wire from a mig spool. It is emphasized cleanliness, inside wall, out side wall, wire and root face to be mechanically cleaned and wiped down with acetone.