Advantage of gas welding aluminum, over tig welding. 1

[hemi43]

I'm a tool&die maker with a home workshop near Toronto. I have been fabricating items for many years, but have found that I am getting more and more into custom motorcycles. I have a tig welder, (Hobart tig wave 250)and can lay a pretty nice bead on aluminum. I was watching a show on TV about a guy who builds one of a kind motorcycle tanks out of aluminum, but he gas welds them together. He also owns a tig, but uses Oxy-Acetilene instead. Why?? Is it stronger??What is the process?? What filler rod do you use??What base metal do you use?? Thanks.
Any reply would be appreciated.

 

[ornerynorsk]

Tig welding is really the way to go. Gas welding aluminum is damned difficult for the novice. You need cobalt blue goggle plates in order to see puddle phase transition of the weld-melt. Some people (especially highly experienced craftsmen) tend to do things that seem difficult to an outsider. It adds to the intrigue of the process, and therefore makes it more "valuable". Not to say you can't or shouldn't learn to gas weld Al, but it is hard until you've got it mastered.

 

[mcprofusion]

Sounds like he's Braze Welding. Different filler metals are available for this process. I can see it being faster than Tig Welding.

 

[ornerynorsk]

it's not brazing, it's actually welding using aluminum filler. This is an art that started going out 30 or 40 years ago, and there are precious few people who can do it anymore.

 

[mcprofusion]

I concur with "ORNER", brazing Al requires a different skill approach. There is a small difference between the melting point of the brazing alloy and the base metal.

 

[jeffita]

I worked in aerospace here in so ca. on and off
since the early 80s, and up until my final layoff
[dec.99] mcdonnell douglas/boeing still oxy/hydrogen
welded low pressure tanks and air ducts with that process
I was certified in that process and didnt consider it
too difficult.
When i asked our eng. support why that process over tig
i was told that oxy/hy was more cost effective for the material and joint design than tig
I.E. on burndown flange and butt welds it was virtualy
impossible not to obtain complete penetration.

As far as filler metal, it was the same as tig, 4043
. cant recall if any oxy/hy welded parts
ever went to anodize. but then i guess like tig you would use 5356.

Now i build drag race cars and yes, i tig my tanks together.

I use 3003 as the base metal and 5356 as the filler metal.
The tanks are not pressurized and seem to last forever.
Im constantly upgrading tanks that were built with the 3003/
5356 that are 15 to 20 years old and are still in use!

 

[TVP]

Parts of the following are taken from ASM Volume 6 Welding, Brazing, and Soldering:

The oxyfuel gas welding (OFW) process uses a flux and either an oxyacetylene or oxyhydrogen gas flame. When the oxyacetylene flame is used, a slightly reduced flame is required, which causes a carbonaceous deposit that obscures the weld and slows the travel speed. The visibility, control, and weld speed are obtained when an oxyhydrogen flame is used with aluminum alloys.

The flux is composed of fluorides and chlorides, and must be removed after welding to avoid corrosion in service. For this reason, GTAW has generally replaced OFW of aluminum alloys. The use of a flux limits the alloys for which it is suitable (basically only 1XXX, 3XXX, low solute 5XXX, and 6061/6063) and produces the greatest heat input. This results in the lowest mechanical properties and highest sensitivity to weld cracking with heat treatable aluminum alloys. The advantage of the OFW process is the low equipment investment.

Care must be taken in order to insure a reducing atmosphere, as oxygen uptake creates extremely brittle welds. It is extremely difficult to obtain a neutral oxyhydrogen flame by the visual methods of flame adjustment. The oxyhydrogen flame itself is scarcely visible, and no combustion zones, typical of the hydrocarbon gases, can be determined. To avoid an oxidizing flame, excess hydrogen must be present. Since there is no carbon in the gas, the temperature is several hundred degrees lower than a neutral flame. A ratio of 4:1 hydrogen to oxygen is typically used.