Brazing Aluminum | GTAMotorcycle.com

Brazing Aluminum

nobbie48

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Aluminum is tricky to work with particularly if you are inexperienced. Serious life affecting stuff should be left to the pros but sometimes one runs into a cracked cover, ornamental item etc that needs to be put together and pop rivets aren't the way to go.

Youtube shows a bunch of different products with different claims but all of the demos I see have the same limitations. The products sometimes say "Welding" but they are actually using a lowish temperature alloy which is brazing or soldering.

Typical problems are:

Overcoming the instant film that forms on bare aluminum.

Doing a vertical braze line.

The thermal conductivity of aluminum is such that you can't tack stuff with brazing rod

No colour change to give a hint of temperature.

The good part is that most of the products don't need expensive equipment, just a propane torch and a stainless steel brush.

FWIW it tried the Bernzomatic rods from Canadian Tire and they seemed to work OK but they were pricey at $4.99 for a pair, about a foot long each. OK for a small repair but I wouldn't want to be building an aluminum boat.

Also, almost all pieces of aluminum are alloys and each will have different weld / braze characteristics. One day you look good the next not because you scavanged different alloys for the project.

Has anyone tried any of the other brands of brazing rods?
 

crankcall

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I'm sure there are real welders on this site and they should be along shortly. I've tried all the brands of aluminum welding rods, even the ones at the sportsman show where the guy welds a pop can. They all seem to be a similar alloy mix and all work the same, its a great bandaid fix and fixed some holes in a sailboat mast, a leak (puncture) in a pontoon boat and a BBQ part , but all were non critical components and its not a true fusion weld , at best its a high end solder joint. I can do a vertical and horizontal weld, but I had years of autobody work standing on my head brazing (old school). I'm not using it ever for a weld that should be certified.
 

nobbie48

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I'm sure there are real welders on this site and they should be along shortly. I've tried all the brands of aluminum welding rods, even the ones at the sportsman show where the guy welds a pop can. They all seem to be a similar alloy mix and all work the same, its a great bandaid fix and fixed some holes in a sailboat mast, a leak (puncture) in a pontoon boat and a BBQ part , but all were non critical components and its not a true fusion weld , at best its a high end solder joint. I can do a vertical and horizontal weld, but I had years of autobody work standing on my head brazing (old school). I'm not using it ever for a weld that should be certified.

Agreed, for use where a failure would only be an inconvenience. I couldn't get a vertical joint to stop running. Maybe I'll try the standing on my head part. :)
 

Spyug

Well-known member
I have a supply of the Alumiweld rods I bought in the States a few years ago. I found them difficult to use as they require the parts to braze to be at and keep constant temps of 700deg + for the rod to flow. Very hard to do with propane. Difficult even with Mapp gas as aluminum doesn't retain heat well. As I am contemplating using them on a project to make mirror perches I was reviewing Youtube vids and found one that suggests getting the part up to temp using a barbeque makes it much easier. I will try that this time.

I agree that these products should only be used on non life critical parts.
 

nobbie48

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There are bunch of videos but one threw in a different trick, scratching the molten puddle with a screwdriver while keeping it hot. I tried it and it seemed to help. Other tips include a wipe down with acetone after the brushing with the stainless wire brush.

I also have some Kester aluminum solder and it seems to work but from a strength standpoint I would only use it for an ornament that sat on a shelf.

Another point to be considered is that the metalurgy of aluminum is very tricky. Annealing, tempering, change the strength and structure of the base metal. A braze job could work for a while and then fail due to fatigue.
 

viccont

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Brazing is a pain in the arss method + its a 19 century technology, tig and mig is the way to go.
 

Spyug

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Brazing may be a pain in the patoot but in the case of nickel/bronze brazing it still produces a very good weld. So good in fact, many of the custom frame builders prefer it over mig or tig. I remember, back in the days of dinosaurs, our shop teacher stated (and I've heard this echoed by professional welders) that a brazed "weld" is stronger than an electric weld. I don't rally know but there must be something to it.

As for this stuff, it is not nearly strong enough for structural work but could be fine as a cosmetic filler or for joining non structural parts.
 

JohnnyP636

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Tried this years ago and the products sucked, the braze/weld was no stronger then a crazy glue. I played around with it then tossed it all in the garbage, I use a TIG welder down the street from me that is great with aluminum cast or billet. So there is really no point in me messing with other methods
 

viccont

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For heavier alloys like copper, bronze/brass brazing could be an option but if it comes to aluminum nothing beats tig/mig. I could spend 20sec making 2" tig weld vs guy who will braze 2" for 20min.
 

Spyug

Well-known member
Well I won't disagree about Tig and Migs but I guess this stuff isI for the home user doing light duties or for folks that don't have access to heavier equipment or can't justify the cost of a pro. I'm going to try it again but my project is not structural or heavy duty so it should work well enough, if I can get high enough temps.
 

nobbie48

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Here's a pic of 1/2 X 1/2 X 0.060 tube brazed with Unibraze from Princess Auto. The joint doesn't look obscene and the failure of the braze came as the tube bent so OK for nonstructural in my books. If this was square bar instead of tube then not so good.

So if you're making a pencil holder out of aluminum for your desk and don't want to spend $3K-$4K and take a five year welding program try brazing.

I used the new MAP gas and it worked. Propane I think would have as well but it was really slow so I switched. I got not quite as good results with the Bernzomatic rods from Canadian Tire but I think it was more technique than the rods.

I also tried All-state rods that I had in the shop for more than a decade and they were hopeless. I used them years ago and got good results but I suspect that the flux core has gone off, dried out etc.

I also played with Kester aluminum solder and while it seemed to stick it would be more appropriate for aluminum foil. I also noted that the flux core in it was leaching out of the solder so long term corrosion issues should be addressed if using flux core materials.
 

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