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So what is the secret to brazing aluminum and what kind of brazing rod do you use for that, I'm curious?Note: In all the options below, you need to thoroughly clean the surfaces to be brazed beforehand with a degreaser and sand down those areas to remove the aluminum-oxide film.Option 1 Low Temp BrazeIf you dont need a high-temperature braze (~1100F), you can choose to use any number of low temperature (~730F) zinc-based-brazing rods. These rods are similar to the rods sold at flea markets and demonstrated to join aluminum pop cans together or to fill holes. I bought a pack of 1/8 inch Hobart Aluminum Brazing Rod at my local Tractor Supply Company (TSC). In general these rods are 93% zinc, 4% aluminum and 3% copper and melt at 728 F.To heat the work piece, you can use a propane, map or propylene gas torch. I found propane to heat too slowly and switched to BenzOmatic MPS gas in my old BenzOmatic Jet Torch. Likely one of the newer swirl torches would be even better.A big advantage of the low-temperature zinc-based rod is that no flux is required! This also means there is no flux residue to clean up and that is a real time saver. To braze with the zinc-based rod, you clean up the work piece, heat it up broadly, and occasionally try dragging the rod across the joint. When the piece is hot enough, the rod melt nicely along the joint - just like soldering. It's really quite easy to do. The result looks good and there is no clean up after.Option 2 High Temp BrazeFor a proper high-temperature, you can use special aluminum-brazing rods like 4047 (88% aluminum and 12% silicon) that melts in a narrow 10 degree temperature range (1070-1080 F).In comparison, two common aluminum rods/wires used for TIG/MIG are:4043 - (94% alum and 6% silicon) that melts from 1065 to 1170 F.5356 - (94% alum, 5% Magnesium, 0.4% iron and 0.25% silicon) that melts from 1060 to 1175 F.At what temperature do some common aluminum alloys melt?1100 aluminum = 1190 to 1215 F6061 aluminum = 1080 to 1205 F6063 aluminum = 1140 to 1210 FSo with 4047 aluminum brazing rod, we are brazing at a temperature that may be within 10 to 130 degrees of the melting point of the aluminum-alloy work piece. This means you have to be gentle, gradual and careful with your heating... else you will have your work piece slump and blob! So how do you do this?Clean the part, apply a special liquid flux to the areas to be brazed. Heat up the work piece. Use a rather gentle oxy-acetylene flame (neutral/slightly reducing) at a distance, wash the flame over the entire area to be brazed. Keep the torch moving! As the base metal heats up and gets close to melting, if you let the torch linger too long in one spot, you will melt a hole or carve out a channel. As the temperature rises, the water-wet flux will dry out first to a white powder, second to a grey powder and finally to a wet grey liquid you are close now. Try dabbing the filler rod onto the joint. When the temperature is high enough, the dabbed filler rod will begin to melt when brushed across the joint. Continue to wash the flame along the joint... until you can simply swipe the rod along the entire length of the joint and it simply melts into the joint. Stop, you are done. Ive done 1/16 inch and 1/8 inch aluminum with this process; I still need to be more careful and consistent with evenly heating the entire joint.Once the work piece is cool enough to handle, you have to get that nasty fluoride-based flux off else it will absorb moisture, become a liquid mush and eats up your work piece. The recommendations are for hot (almost boiling) water and vigorous scrubbing with a small fiber brush. Personally, I find it a challenge to get all the flux off. I found that using one of those hand held steam cleaners (like a small kettle with a long nozzle) worked best.While high-temperature brazing is a challenge, it can be done with a little practice - and it makes a strong joint.continued on next post...Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:Option 3 - High Temp Braze (Rush Job!)Suppose you need a high-temperature braze on some aluminum pieces right now. You may find that your local welding stores dont have the special aluminum welding flux in stock, nor do they have any 4047 aluminum-brazing rods. All special order and takes weeks to get it.What can you do? Most local welding supply stores do stock small packs of stick electrodes designed for stick-welding aluminum. Buy them and make a high-temperature (1100F) braze.Crumble the flux coating off the electrode, mash it up to a powder and mix it with water. Brush this wet flux onto the surfaces to be joined and onto the de-fluxed electrode this will be your filler rod.Using an oxy-acetylene torch, follow the heating instructions in Option 2.When the temperature is high enough, the dabbed filler rod will begin to melt when brushed across the joint. Add a little heat from the torch and follow the rod tip with the flame along the joint. Repeat this until the rod tip melts and flows nicely into the joint.The photo shows the results of such a braze made using Hobart Aluminum 4043 Stick electrodes. Easy on me... this was my very first attempt at high-temperature brazing. It worked but it was a challenge to control and the result, while solid, was not too pretty!Still, when you need it done today, its an option to be aware of.Once again, you need to remove the corrosive flux residue from the work piece.There you go, some Aluminum Brazing Options.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:WELL DONE SIR good job , great infonow ya need a stickyidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:Praise on aluminum, coming from the 'Prop-Doctor' is Praise Indeed!...?... so, what's a sticky? Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:it all has its place, was gas welded long before ,,,,heli'arc /-tigidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:Rick V - Thank you for the tutorial, and kudos for the presentation pics. Can you sight or show pics of your most common applications. OPUS
Reply:The Hobart low temp brazing rods work quite well on thin gauge AL. I use them especially when I am trying to recycle old road signs into instrument enclosures, which I have difficulties Tig'n. They take alot of heat to bond properly though!
Reply:excellent job and write up, i just learned something and may now be able to fix something on a boat, could not get in a tight spot with the tig gun, after some practice. thanks.timJust some stuff in my shop.
Reply:Great write-up and info, Rick! I'm a fan of the zinc-aluminum braizing rods as well. Love how you don't need flux with them.
Reply:Thank you for a great "How To" Rick V!Great pics and explanations.Information like this could be a life saver for many of us.
Reply:Option 4 - High Temp Braze (Swirl Torch / 4047 / Flux)In a recent thread, http://weldingweb.com/vbb/showthread.php?t=48365, I described the high performance of the new swirl type torch using air & propylene gas. I wondered, would that have enough heat (temperature and BTUs) to braze-weld aluminum? Turns out, it does... if your piece is small enough!Using the propylene swirl torch, I easily melted a hole right through a piece 6 x 1.5 x 1/16th inch thick aluminum. The torch melted a similar size piece of 1/8th inch thick aluminum. With time, the torch started to melt a similar size piece of 1/4 inch thick aluminum. OK, I thought, if its about good enough to handle one piece of 6 x 1.5 x 1/4 inch thick aluminum, would it be able to braze-weld two pieces of 6 x 1.5 x 1/8th inch thick aluminum?Heres the kind of torch and result I am talking about 4047/flux high-temperature braze of two pieces of 6 x 1.5 x 1/8th inch thick aluminum. Note: You can see the remaining 6 inches of my 36 inch 1/8th inch diameter 4047 filler rod; I used way too much (my first time).I used the same pre-cleaning procedure described in Note 1 and the 4047 aluminum-brazing rod and special aluminum flux as in Option 2. The air/propylene torch just doesnt have the high temperature of an oxy-acetylene torch, so you dont have to be so gentle, gradual and careful with your heating. I found I still had to be cautious in the corners... and, being my first time, I did get some undercut and slumping in those locations... as the heat cant get away so easily.The flux reacted differently to the propylene swirl torch. The three oxy-acetylene stages of white powder to grey powder to wet grey liquid were not so clear. It took a lot of localized heat to finally obtain the wet grey liquid needed for proper flow of the aluminum filler rod.I kept dabbing the filler rod onto the joint. I noticed the rod would melt and blob/flow onto the vertical plate. With more time in a local area, the rod would melt and blob/flow onto the horizontal base plate. BUT... the two horizontal ribbons of molten metal (on the vertical and on the horizontal base plate) would not flow together! It took a lot more heat and flame movement of the molten metals until yes, they finally flowed together forming a joint! At one point, most all the molten metal ran into the two corners and gathered into large pools; later it flowed back along the joint quite quickly once I got the center portion hot enough. Wow! This was so unlike oxy-acetylene there you could gently heat the whole piece up and then simply swipe the rod along the entire length of the joint and the rod easily melted into the joint. With the 'swirl' torch, I had to work in more localized areas - focussing on one region at a time.Remember to use hot water & a scrub brush to get that nasty fluoride-based flux off else it will absorb moisture, become a liquid mush and eats up your work piece. With this particular swirl torch (BernsOmatic TS839) operating with 99.5% propylene gas, joining two pieces of 6 x 1.5 x 1/8th aluminum is just about the limit of the torchs capability.I would conclude that if you have small pieces of aluminum to be joined, this approach would be useful.Its really quite inexpensive. I bought my torch/gas for about $35 on sale, the 4047 rod was about $8 per pound and the 8 oz can of special aluminum flux was about $12. Hey, $55 isnt too bad an investment to high-temperature braze/weld aluminum. Sure it doesnt compare to the better results possible with oxy-acetylene, MIG with argon or TIG with argon... but then too, they dont high-temperature braze/weld aluminum for a total investment of only $55!There you go a 4th Option for brazing aluminum.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:good write-up well donerick cut ya cut one so we can see inside?idealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:Originally Posted by prop-doctorrick cut ya cut one so we can see inside?
Reply:nope was just wanting to see how it flowed guess any one, just pick the best or worstidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:Originally Posted by prop-doctor... just wanting to see how it flowed guess any one, just pick the best or worst
Reply:thanks rick looks like it flowed pretty good again thanksidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:Originally Posted by prop-doctor... looks like it flowed pretty good
Reply:if you can run a bead on bead on bead till the missing metal is back, then grind down to blade thinkness and it balance out in weight,maybe .but will the next repair blend with 5356 or 4043 if tiggedthe stuff like you used before won't weld over (or blend) with tig rod i have to remove any trace of it (if some one else reapir using it)idealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:Originally Posted by prop-doctorif you can run a bead on bead on bead till the missing metal is back... but will the next repair blend with 5356 or 4043 if tiggedthe stuff like you used before won't weld over (or blend),,, i have to remove any trace of it
Reply:still a good write uplets others know that it brazes well/goodit is by no means welding guess it could be said, a one time repair till said part can be replacedidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441 |
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发表于 2021-8-31 23:30:59