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Up Topic Welding Industry / Technical Discussions / D17.1 RT failure (Porosity)
- - By TRC (***) Date 04-25-2006 00:08
I'm doing 3.5" dia, 6061T6, .050 wall tube. Filler 4043, straight argon, 3/32, 2% thor. Power source is Miller Aerowave. Torch is water cooled CK in new condition. Parts are roll welded in the flat position.
I've tried many setting on the Aerowave from one end to the other. The best results have been right about the middle but still no cigar.
I've just finished a Titanium job without any indications of gas contamination so I don't think it's that. Parts are cleaned with acetone then Scotch bright and wiped a second time. I tried welding one side with internal purge. I tried welding inside and out. I even tried welding inside and back gouging outside. If anyone has experianced this and knows what the fix is would you be so kind as to give me a phone call at 410-808-8353 Thank you Ted.


Parent - - By Lawrence (*****) Date 04-25-2006 21:23
Ted

Lots of possible fixes.

Is the work anodized prior to welding?


There are lots of threads on this subject here... Try a search of Aluminum GTAW or X-ray and you will find a bunch of info.

Please forgive if this sounds over simple.... Were the indications Bright or Dark... If the indications were bright than the problem is not porosity but scattered tungsten... Just a shot in the dark:) but have seen this mistake before.

Next, your tube should be prepped with abrasive (I like a 120 grit aluminum oxide flapper), this needs to be done just prior to welding or the parts bagged after prep. Remember also to prep the faces of your pipe, any resudual burrs will catch oil etc and bring hydrogen into the picture.

No root gap... faces should be tight.

6061 is also soluable to Hy, the Hydrogen usually escapes as the weld freezes, however if the work is overheated more Hy will dissolve into the weld than can escape and this can be interpreted as fine porosity (usually found in greater quantities near weld terminations) Decreased amps, increased travel speed, increased wire size to cool the puddle or a combination of the three may be effective.

Yeah, in my opinion, Aerowave is no real advantage in the configuration you are describing unless you are trying to really produce high quantity via some form of automation (which Aerowave is not particularly friendly to by the way). Normal settings ought to be just fine.

Also keep in mind that with Aerowave your balence control is a *percentage* up to 90% EP. So when you have your Aerowave set at about 72 it is approximatly equivelant to your synchrowave set to 10 (max penetration) Therefore, when you go past about 75 you will need absolute perfect surface prep and possibly a slight bump in EP amplitude to provide sufficient etch.

If your torch is water cooled, you might consider loosing the thorium and move to a full length 1/16 cerium or zirconium electrode. Neither Cerium or Zirconium tend to spit across the arc plasma or distort at the tip like thorium will when overheated.

You ought to be able to get D17 quality welds in aluminum tubing with no purge.

Parent - - By TRC (***) Date 04-25-2006 23:37
Hey Lawrence, thank you. My first experiance with digital RT. They can make the view black on white or white on black!!! The tech says it's not tungsten it's porosity. I think the over heating may be a big part of what's left of my problem. I did two more today and there was porosity in the area that had signs of penetration on the inside of the backweld. Thanks for you help- I'm getting closer- TED

PS I tried to get them to change the code to API 1104- they didn't think it was funny!@#$%
Parent - - By Lawrence (*****) Date 04-26-2006 01:20
Ted,

No need to change code... You have a process control problem, and when you solve it these welds will be almost automatic.

0.050 is just to thin to require a backweld. This should be a single pass full pen type of production weld.

Are you rotating your tube mechanically to keep the weld at Top dead center or are you doing several stops and starts to remain in the flat position?

Remember; with aluminum that the melt thru and overall profile on single pass welds are going to be typically larger than with steels, titanium or superalloys. Do not fear this as it is *typical.* Starving your joint of filler in order to get minimum profiles can be the cause of problems like you describe.

Is the porosity scattered evenly? or clustered at specific points, and if so how large are the clusters?
Parent - By TRC (***) Date 04-26-2006 23:42
I got it! Took your advice and did it one side with a purge. I was cleaning it with scotch bright and just shining it up by hand. That wasn't enough to cut the oxidation. I have a low rpm die grinder and some very smooth burs. When turned very slowly they clean the oxidation very nicely. After taking it down to bare material and changing the settings on the Aerowave I got a perfect weld. The settings are 100 on the freq and 60 balance with the amps equal on both sides of the wave.
That digital RT is amazing. The tech was showing me some electrical components they were checking and it was really cool to see what it''s capable of. It's more like an RT microscope.
Thanks again Lawrence- I was only kidding about the code- TED
Up Topic Welding Industry / Technical Discussions / D17.1 RT failure (Porosity)

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