A Bugatti fender

[Peter Tommasini]

Originally Posted by keith

Whatever this is worth. I read sometime ago....I believe it was mentioned by Ron Covell....that the top custom motorcycle tank builders had concerns about tig welds leaking.

Where ever is possible I rather gas welding ally (whether it's a bike tank or a car panel) over tig for many reasons

This is only my opinion
Peter

[Steve Hamilton]

Kerry correct this if it is wrong!

The TIG joints on this fender were done using 1100 filler and welded on both sides. The CP planishing hammer was used to stretch the weld zone back out, prior to metal finishing.

1100 rod with 3003 H 14 sheet makes a soft weld zone

Steve

[Kerry Pinkerton]

Yes, 1100 rod. Planished with the CP planishing hammer and filed.

Guys, this is a fender, not a tank. I acknowledge that a gas welded seam is more workable than TIG because I've observed tests where each type was worked to failure. HOWEVER, in both cases, it took a good bit of bending and shaping work before failure. For someone who gas welds aluminum frequently, there probably isn't a reason to TIG. For the rest of us however????

I'll let everyone know if the TIG welded fenders fall off my roadster.

[RockHillWill]

The same issues that contribute to inclusions resulting in leaking are also in a position to allow less resistance to cracking from vibration. In addition to the tank/leak issues, TIG welded front and rear spoilers were repaired and replaced often due to cracking, often adjacent to the welds similar to MIG welding.

I am in NO way suggesting that one type of welding is ALWAYS better than any other type of welding, and it would seem that preparation prior to welding and use after the welding play a huge part in what to expect. I was only suggesting that experience and knowledge combined would seem to widen the field of vision from which to make a choice.

My mediocre skills at both TIG and gas welding would make my choice seem insignificant, but a person seeking high quality craftsmanship would seem to want to make decisions from the largest field of information possible, and I am stepping up with what little I do understand at this point, being optimistic that others might make corrections and/or add to my information collection.

I have a HUGE collection of opinions, I was more looking for pertinent information that I might add to my smaller collection of actual knowledge.

[Steve Hamilton]

Will
I agree completely!
I was not trying to suggest that TIG was better, just thought that members reading the post should be informed of how to get a more ductile weld by using a softer alloy rod when using the TIG process.
Proper cleaning of sheet and filler are required with both Oxy and TIG

Steve

[John Francis]

Originally Posted by RockHillWill

I have a HUGE collection of opinions, I was more looking for pertinent information that I might add to my smaller collection of actual knowledge.

The following links have some "food for thought" on the welding questions.

"gas" entrapment
http://www.twi-global.com/technical-...um-any-advice/

filler choice
http://www.esab.ca/ca/en/education/b...num-alloys.cfm

"mushey" cooling stages
https://www.uwgb.edu/dutchs/Petrology/beutect.htm

[Z5Roadster]

Ha Guys I'm sorry to have stirred up a hornets nest, I have great respect for Jim, a very clever hard working tradesman. I asked the question because to my knowledge we have never had a panel with both types of welding carried out by men at the top of their skill level to compare one against the other.

Should the day come when I have an aluminium panel requiring welding I will go with gas but I think a lot of us use what equipment we have and if the process is mastered we stay with it.

Think we should stay on topic. Thanks gents.

[RockHillWill]

Thanks John. That is good, useable information. Thank you for posting!

[AllyBill]

Only time I've seen cracking problems with TIG is when the welder sets off without giving the material enough pre-heat. It's too easy just to give it lots of pedal and set off down the bead because of how quickly you can get the heat in but the result is that it quenches itself from the surrounding material and you get brittle welds until everything comes up to temp. Not so with O/A because the heat goes in that bit slower.
Put a bit of preheat in before you arc up and your TIG welds will give no trouble.

Will

[crystallographic]

Originally Posted by John Francis

The following links have some "food for thought" on the welding questions.

"gas" entrapment
http://www.twi-global.com/technical-...um-any-advice/

filler choice
http://www.esab.ca/ca/en/education/b...num-alloys.cfm

"mushey" cooling stages
https://www.uwgb.edu/dutchs/Petrology/beutect.htm

My brief and quick comments to those three links:

Gas entrapment is also explained very simply and graphically in the aluminum foundry, where the molten aluminum in the crucible is not ready to pour until "degasser" is added. When the degasser is plunged into the 1250F moilten aluminum there occurs a sudden violent boiling, a gas cloud rises, and the level of the molten aluminum drops, by 10 to 25%. (Aluminum welding flux is an excellent degasser, by the way.)

Volume down = density UP, by the way.

I can tell how well-versed the technical writer for ESAB is here when he actually mentions a brazing filler (4047) as a welding solution.

Further, making mention of aluminum alloy 2219 should also include its designed usage: ballistic material. So for those of you making bullet-resistant enclosures, be sure to follow along there.

Gas-entrapment of tig-welded aluminum is part and parcel of that welding process, and as the president of the Aluminum Association told me specifically, "it is going to be with us for the foreseeable future." Simply electrically melting clean aluminum in a clean crucible in a clean enviroment can create gas entrapment, so get ready for the real world welding of the same metal in the fab shop, body shop, or art studio.

Re: Wil's statement about the over-the-road truck tanks - I had a long conversation, in person, with several techreps from one of the biggest OTR truck tank makers about 12 years ago - and they were at their wits' ends with leaks - with their clean-room environments, cameras inside the tanks, precision-controlled methods, fillers, back purges, preheat, postheat, pulse, throb, vibration-induction, and all the rest. Leaks, leaks, leaks on perfect-appearance welds inside and out. I simply told them what my solution would be - use appropriate technology that never has a porosity problem - gas welding.

And I gave them an AGW demo, complete with the "TM postweld destructo test."

And I told them to simply do what I learned from personally nudging the techreps at the Aluminum Association (ALCOA, Reynolds, ALCAN, and Kaiser guys, actually): make your tig weld nice and long on clean material, just like in your tank-welding environment. Cool the weld, and then simply run a band saw right on down the center of your weld, splitting halfwise along the length. Acid etch to clean up particulates. Eyeball results in good light.

What you see is exactly what you get. Swiss cheese down the center of the weld. (Need a degasser?)

I never heard back from them, but it's interesting to note that they changed "back" to gas welding.

(But I hear that if you spend $10-12K on the newest tig machine that you stand a better chance of lessening the cheesy centers.
So, there is hope in the new dawn. )