The filler metal is distributed to the closely fitted surfaces of the joint by capillary action. The various brazing processes are described below. Torch brazing is performed by heating the parts to be brazed with an oxyfuel gas torch or torches. Depending upon the temperature and the amount of heat required, the fuel gas may be burned with air, compressed air, or oxygen.
Commercial brazing filler metals for aluminum alloys are aluminum base. These filler metals are available as wire or shim stock. A convenient method of preplacing filler metal is by using a brazing sheet an aluminum alloy base metal coated on one or both sides.
A third method of applying brazing filler metal is to use a paste mixture of flux and filler metal powder. Common aluminum brazing metals contain silicon as the melting point depressant with or without additions of zinc, copper, and magnesium.
Aluminum brazing fluxes consist of various combinations of fluorides and chlorides and are supplied as a dry powder. For torch and furnace brazing, the flux is mixed with water to make paste. This paste is brushed, sprayed, dipped, or flowed onto the entire area of the joint and brazing filler metal. Torch and furnace brazing fluxes are quite active, may severely attack thin aluminum, and must be used with care.
In dip brazing, the bath consists of molten flux. Less active fluxes can be used in this application and thin components can be safely brazed. If you want to cool the pipe and try again, pick up with a tool and place in water a process called quenching a weld water will weaken a weld, but for practice it is fine.
Brazed joints should be of lap, flange, lock seam, or tee type. Learn more about these joints here. Tee joints allow for excellent capillary flow and the formation of reinforcing fillets on both sides of the joint. For maximum efficiency, lap joints should have an overlap of at least twice the thickness of the thinnest joint member. In this case, the use of straight grooves or knurls in the direction of brazing filler metal flow is beneficial. Closed assemblies should allow easy escape of gases and in dip brazing easy entry as well as drainage of flux.
Good design for long laps requires that brazing filler metal flows in one direction only for maximum joint soundness. The joint design must also permit complete post braze flux removal. Whenever possible, parts should be designed to be self-jigging. When using fixtures, differential expansion can occur between the assembly and the fixture to distort the parts.
Stainless steel or Inconel springs are often used with fixtures to accommodate differences in expansion. Fixture material can be mild steel or stainless steel. However, for repetitive furnace brazing operations and for dip brazing to avoid flux bath contamination, fixtures of nickel, Inconel, or aluminum-coated steel are preferred. Pre-cleaning is essential for the production of strong, leak-tight, brazed joints. Vapor or solvent cleaning will usually be adequate for the non-heat treatable alloys.
For heat-treatable alloys, however, chemical cleaning or manual cleaning with a wire brush or sandpaper is necessary to remove the thicker oxide film. Furnace brazing is performed in gas, oil, or electrically heated furnaces. Continuous circulation of the furnace atmosphere is desirable since it reduces brazing time and results in more uniform heating.
Products of combustion in the furnace can be detrimental to brazing and ultimate serviceability of brazed assemblies in the heat treatable alloys. I bought lots of attachments for it for the fame end. I have some of those rods but I have never tried them.
Watching this video may get me motivated to give it a shot. I also have the spool gun for my mig, and I have yet to try that. I thought I would be playing with more aluminum but as it turns out I play with a lot more sheet metal. These rods produce a really weak joint. Get a bottle of argon and get your spool gun going if you want to weld aluminum for real. It does take practice and buy a bunch of spare tips for the gun. One tip, if the wire burns back to the tip and welds to the end, just toss the tip.
Do not try to clean it out and reuse it. It just does not work. Once the molten aluminum wets the tip its all over with. Yet people here are merrily mixing these very elements. The oxygen in the rust reacts with the Al. Too dangerous without serious safety protocols in place. Also just about the worst thing to watch without proper eyeware…. Also even with the proper mix igniting thermite is hard, very hard. You will not do it with a normal torch without an intermediate such as magnesium thin material like a ribbon — solid magnesium is hard to ignite too.
From to Schwinn made fillet brazed bicycle frames with Cro-Mo tubing. The reason they quit making them was the labor to braze, smooth and finish all the joints to prep for painting got to be too expensive. Further to this — yes, up to the 80s, the aspirational bike frame was special double-butted thicker wall at the ends, thinner wall in the middle chromoly tubing, lugged together and brazed.
I have one nice lugged frame. I know a lot of aluminum frame bikes are still welded by hand. Used to do service calls to a place that built them for some pretty big names.
There was this time I took a job fixing the air conditioning system on a tug boat in dry dock. They were fascinated by the idea of connecting joints with such relatively low temperatures. TIG brazing can be done, but it is not easy.
The heat is concentrated in too small of a space and temperature control is really hard. I have done some of it for filling holes and gouges in steel prior to powdercoat. If I had an oxyfuel rig, I would definitely use it instead. I went down to Home Despot, picked up a couple of these brazing rods and tried this. It works pretty well. When I raced Formula E karts mph in 3 seconds and top speeds in excess of mph the preferred method of repairs and chassis build was to use bronze braising.
The bronze give great strength where there are constant stresses. I think this is one of the most significant information for me. Thank for sharing! My husband uses a lot of aluminum at his job in the industry and asked me to help him find tips on how to do brazing. We love how you talked about how it can come apart but is good for smaller jobs. These tips will be useful as we search for a professional to help him with his aluminum brazing.
Not a big deal. This top yoke is still good after ten years of racing.. I would definitely use again in thaI way. Please be kind and respectful to help make the comments section excellent. Comment Policy. This site uses Akismet to reduce spam. Learn how your comment data is processed. By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies.
Learn more. Report comment. No… the host metal is not melted in brazing. Got any recommendations for reading material? Sounds interesting. It is insanely easy! The biggest difficulty in all this is that it takes a lot of heat; you need a good torch! Be sure to keep the torch moving to avoid overheating the aluminum or remelting the filler rod.
After completing the braze, allow the part to cool naturally. When the part has cooled, Super Alloy 5 flux residue can be easily removed with a wire brush. The original part can then be powder coated, painted, polished, drilled, tapped, bent, threaded, anodized or machined. Related Product s Sale!
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