Aluminium Soldering / Brazing ?

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Hi,I'm new to all thisOk, I bought a BernzOmatic Aluminium Brazing & Welding RodI heated it up with my small butane hand torch.I have two pieces of aluminium clamped together that I need toput a seam/bead down the middle so they are soldered together.But when I heated up the rod and metal, the rod melted,but it would not stick and/or flow to the other aluminium metal. I couldnot get it to stick to the aluminium.How to I solder aluminium together using these rods ? Thanks,
Reply:Ok, here's what I've found out so far...Tin the aluminum under oil, then solder as normal.Aluminum normally won't accept regular solder. That's becauseof the oxide coating on its surface. By covering the surface withoil, you can scrape away the oxide coating while preventing oxygengetting to the surface and reforming it. You can then tin the surfacewith an iron, through the oil coating, and get a proper bond. Thenyou can clean the oil off and solder as usual.This is a home shop technique. There are probably better solutionsin a production environment.But what does it mean to Tin the aluminum under oil ?How do you do that ?Thanks,
Reply:A butane torch might have been to small. Try a regular propane blow torch. After proper cleaning heat the metal and let the heat in the metal melt the brazing rod. Keep the rod near the flame but do not heat the rod directly from the flame. Make sure that the aluminum is not anidized.
Reply:It's sounds like you need to heat up the base aluminum a lot more.
Reply:Is the rod flux coated, if not you defenetly need flux, wont work without it!
Reply:you can buy cans of flux or flux coated rods
Reply:Can you think of a different way of getting your assembly job done?  I've used perhaps a dozen "Aluminum Soldering Kits," over the years, following directions very carefully, using various gas/electric heating methods, and I have NEVER gotten a good solder connection.  Yes, it can be done, but no, not easily in the home shop.  The kits varied from hardware store stuff to the best my local welding shop could supply with uniformly disappointing results.  The specific alloy you are trying to solder can have a strong influence on the results.  I think close to pure aluminum (rare) is easiest for the kits to work with.Never heard of the oil trick, but some of the fluxes are kind of oily looking.  One factor is that the chemicals used in aluminum solder fluxes are extremely sensitive to excessive temperature and will only work over a narrow temperature range between becoming chemically active and becoming inert or destructive of the soldering process from excessive temperature.   It is difficult for the home shop practitioner to maintain such temperature control.  Once it's turned brown or black, you might as well start over from scratch.My impression is that either (or both) inert atmosphere or ultrasonics are best for aluminum soldering.  The ideal would be an ultrasonic soldering iron, i.e., a conventional electrically heated iron that is also ultrasonically excited to break down the oxide layer under the liquid solder.  They are on the market, but at prices you can imagine, and they reputedly work very well for a wide variety of materials.  I have even read reports of "soldering" to glass with ultrasonic irons.Have fun.awright
Reply:My previous answer assummed that you were using the brazing rods. Aluminum solder kits and brazing rods are two different things. The brazing rod that I haved used are bare and use no flux. I have no idea if there's a flux mixed in to the rod or not. There not as good as welding but work very well within their limits.
Reply:My error.  I thought he was referring to a soldering kit, not a brazing kit.  But the problems are related. all having to do with the difficulty of getting past the oxide layer.  I've never tried Aluminum brazing rod.For those interested, ALCOA used to publish booklets on soldering and brazing aluminum.  You might find one in a used book store or by a used book search on the internet.  They make it sound easy.awright