Who Knows Anything About Welding Aluminum?

Factual Questions
1
      • I have a couple small projects that require the welding of metal. As it happens, I wanted to use aluminum for both. I dunno squat about welding, though. A few quick questions:
  • Why is aluminum usually welded with electrical equipment rather than a torch? (Assuming I buy welding equipment, I’d rather get something that can cut material well, as well as join it)
  • There’s stuff available called “aluminum repair rod” that melts with a propane torch that is said by many to be much easier to use, especially for thin aluminum, which is what I am going to use. I found three different companies in the US that make it. I assume it produces joints at least somewhat weaker than a pure aluminum weld, but I can live with that. I can’t find much information critical of it but I don’t know exactly where to look and it’s definitely the least expensive to try out anyway. Is there anything bad about using this rod? - MC
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Mr. L says…

“No, as long as you use a good aluminum flux and make sure your metals are clean, the rod will work just fine.” “You can get the aluminum stuff at any plumbing supply house. You use electrical rather than torch because it is easier to maintain a lower temp and not melt your metal.”

3

There are 3 ways of welding aluminum I’m aware of: Torch & Rod, MIG and TIG.

Torch is the cheapest and will look good if you know what you’re doing. It is easy to heat it to much and the material will melt or deform.

MIG gives you better control. You can use a standard MIG with a aluminum compatible rod and it also uses a different gas than steel MIG welding.

The best way to weld aluminum is TIG. However, they require practice (much more so than MIG) and the quipment is very expensive.

Try the torch & rod first. The weld (if done right) will be atleast as strong as the surrounding material. It is essential that the material is clean for all types of welding. Wire brush until it is all shiny. Also practice on some scrap first.

Markus

4
      • Thanks so much for the answers- Woohoo!!
  • What I meant in the OP was, for what I want to make, I have to make it out of thin aluminum, and I have to be able to weld that thin aluminum together. A past associate who knew better said that this was a fairly difficult thing to do well using an acetylene torch and rod.
    Anyway, -chalk up another success to the internet: had I not searched online, I’d have never known it was possible to weld anything with a $20 propane torch. - MC (happy that projected cost of projects has taken a dive; usually it goes the other way…)
5

Don’t bother with the “aluminum repair rod”. It takes a great deal of effort to get a vaguely tolerable join, and even then, the join is far weaker than the base metal.

If you do try it, remember: Clean, clean, clean. Scotchbrite, a small stainless-bristle wire brush, acetone. Lather, rinse, repeat. Use the repair rod immediately after celaning. If you wait five minites, clean it again. Aluminum almost instantly forms a thin oxide layer when cut or sanded- it’s this oxide that will cause no end of troubles with the cheapie repair rod crap.

MIG- wire-feed welding- is okay for aluminum, but typically requires a “push-pull” wire feed or a spoolgun. You will also typically get “bulkier” welds, meaning they tend to have more metal than necessary.

Using an acetylene torch is possible, and in fact, many old-time English coachbuilders made many a fancy car with that technique. Like some of the original Cobra bodies, old Ferarri racers, and so on.

It makes for a good, self-annealing weld (meaning it’s less likely to crack from fatigue) but there’s a great deal of skill involved. I’d say moreso than TIG welding. Expect a bloody great lot of practice before making a decent, good-looking weld.

TIG is by far the best bet. The tungsten-arc produces a very controllable heat, is very steady, doesn’t produce a “pressure” as the torch gas flame does (meaning it distorts the fragile molten puddle less) and the inert-gas weld shield reduces contamination- thus weakening- of the join.

But, unfortunately, none of the above are the kinds of things you can pick up for the first time this evening, and expect a usable, good-looking part by tomorrow morning. :smiley:

If the project is small, and you’ve already formed the pieces, why not contact a professional welding shop and have 'em TIG it?

6

Resistance welding (“spot welding”) is a great way to weld aluminum together. It doesn’t involve the addition of any new material at all. Unfortunately, not a lot of people have spot welders in their garages, or they’re little, tiny things not capable of aluminum welding. But, if you end up going to a shop, as them about their resistance welding options.

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      • I tried the propane/aluminum rod - it was the cheapest (I got started today for about $25) and it actually seems to join very well if you use the right technique: heating the aluminum workpieces and “jabbing” at the seam with the cold rod. Any other technique don’t work; the rod melts but doesn’t bond with the other metal. The hardware story guy said most of this type of (low-temp) rod they’ve had is fluxless, making it even easier to use.
  • I also was surprised to see that a regular propane torch can melt/burn a hole in aluminum. Not real speedy or cleanly, but still. - MC