#1
|
|||
|
|||
BRAZING --- (not welding) alumiminum
hmmmm where to start?
"Brazing" by industry definition, is hot joining metals at a lower heat than the melting point of the parent metal(s). Brazing is commonly used to join together the aluminum torque converters in late-model cars ... this is accomplished with aluminum furnace brazing. So, to put the three hot joining methods for metals in perspective, by US industry standards: Soldering occurs below 850F (was 725F, then 750F, then 775F, then 800F.... ) Brazing occurs above 850F - and below the melting point of the parent metal. Welding occurs at the melting point of the parent metals. Friction-stir welding uses friction to melt dissimilar metals together. For instance, two metals with widely-separated melting points can be welded in this manner: aluminum, melting at roughly 1240F - depending on the alloy of aluminum - stir-welded to steel, melting at 2400F, depending on the alloy of the steel. Explosion welding is also used for this purpose. Perhaps the most commonly-recognized form of brazing is using brass ("brassing") to join steel and is one of the oldest brazing methods we know of. Attachment 41538 P1160147 copy.jpg Rusty steel joined with silicon bronze - no flux used - (TM Tech) Silver-brazing (1020F to 1550F containing 5% to 55% silver) is used commonly in refrigeration and high-pressure copper and steel gas lines, because it flows very well and has a very high strength, from 40 to 120KSI tensile, depending on the joint design. By comparison, welded steel is 45KSI and up. Attachment 41539 silver braze, fittings, tubes 2 copy.jpg Copper to brass, stainless to stainless, brass to brass - using flux-coated 55% silver solder (TM Tech) Soldering, below 850F, is commonly used to join brass radiators, copper plumbing, and when the solder contains 3.5% silver it is called silver-bearing solder, and is used for potable water plumbing and food industry items. Aluminum brazing was developed by ALCOA in the late 1930's, and has been common for joining aluminum fuel tanks for aircraft, ever since (using the O/F torch). Since brazing does not melt the parent metals, there is no solidus, or re-solidifying of the parent metal from molten to solid, hence: the distortion from that is avoided by brazing. For instance, after WW2, the Crosley Automobile Company in Oakland, California, made a number of small four-cylinder gasoline engines of formed sheetmetal joined by furnace brazing. Yes, no castings - all sheetmetal, brazed together. (The Crosley Hotshot was very popular.) ***** Here is one example of brazing - aluminum tig-brazing - to modify an aluminum heat-exchanger (oil cooler) for an olde Mercedes 300S: (The Behr company has been making aluminum oil coolers for German cars since 1950's ... ? And since they still make the same cores, it is possible to convert a modern version to an early NLA version by whisking off the essentials from the bad cooler with the band saw, and then grafting them onto the modern core.) Thus: P1080517 copy.jpg P1080530 copy.jpg P1080526 copy.jpg P1080523 copy.jpg P1080543 copy.jpg Penetration on the long seams is very acceptable and gives good strength .... P1080539 copy.jpg P1080540 copy.jpg P1080541 copy.jpg P1080536 copy.jpg note the tig-braze is right against the factory dip-brazed seam - with zero melt-back. P1080538 copy.jpg Note again, the undisturbed factory seam. Please also note: these original aluminum heat exchangers are dip-brazed (aluminum brazing by heating the assemblies and dipping them in hot brazing filler material.) I chose to tig-braze instead of torch-brazing because of fast heats - I did Not want to upset any of the original joints and seams. No warpage. No leaks on first test. Perfect fit. My time: 2.9 hours, total. Happy customer and 300S is still the daily driver after 4 years, now. Resources: ALCOA film, "Aluminum Welding Methods" (also includes furnace brazing, dip brazing, and torch brazing of aluminum parts): http://www.tinmantech.com/products/d...ng-methods.php "Brazing ALCOA Aluminum," ALCOA "Welding Aluminum, Theory and Practice," The Aluminum Association (hoping I got my info straight ... ) OH - final thought here - Please do not confuse the HTSxxxx, Lumi-weld, Dura-fix etc etc with real aluminum brazing materials. They are Not. They are high temp. solders, sold incorrectly and expensively for doing "welding and brazing." Caveat Emptor.
__________________
Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. Last edited by crystallographic; 05-01-2017 at 12:22 PM. |
#2
|
|||
|
|||
I always learn so much from you Kent. Thanks again for taking the time to teach this lesson.
__________________
Bill Longyard Winston-Salem, NC |
#3
|
|||
|
|||
Kent, when I did the small worlds fastest Indian sculpture project last year, I used both soldering and brazing for the few connections I had to make. Not a big fan of built-up work like that but that was the project. First silver-brazing and then transitioning to regular lower temp soldering allowed me to stay below temp and not compromise the initial joints when doing subsequent joints. These were steel parts, more mass and longer thermal retention. All was done with o/a gas torch. Pretty common approach to built up work, especially in jewelry.
Would the smaller HAZ of the TIG have possibly allowed more joints to be silver soldered instead of typical solder/braze approach? Is this more effective in aluminum or relevant with other base metals? It would be a good way to make all joints the same strength vs hard and soft solder.
__________________
AC Button II http://CarolinaSculptureStudio.com https://www.youtube.com/channel/UCzSYaYdis55gE-vqifzjA6A Carolina Sculpture Studio Channel |
#4
|
|||
|
|||
Quote:
I don't know about smaller deposition but I surmise that could be a benefit. For myself and the applications I find beneficial are those where I need thorough deposition into fissures, voids, pits, crevices - anyplace leaks can occur, or where plating will find a flaw.
__________________
Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
#5
|
|||
|
|||
Hi,
One of my next projects is building a new wing gas tank for a 1966 Citabria, for a customer. I received in the mail today, an original tank to use as a pattern. The steel gas cap filler neck is aluminum brazed or soldered into the top of the aluminum tank. I would like to learn the process on doing this, as I do more and more work on these older aircraft gas tanks. Bill
__________________
Bill Tromblay "A sign of a good machinist, is one who can fix his F$@& Ups" My mentor and friend, Gil Zietz Micro Metric Machine. |
#6
|
|||
|
|||
Quote:
I was shown this technique by a Northrop welder - it's not an easy technique and can drive someone nuts. Like the various aviation skills, welders would study and then test for fuselage welding, gear welding, motor mounts, aluminum welding, tank welding, and joining aluminum filler necks to the steel neck rings. "Pins" were awarded for each of these skills, and you presented your rating pin and the drawing of the part to the supply office in order to draw correct filler metal and welding supplies for that job. Unmarked, you did not know the type or mfr of what you were given. I have not taught this technique to anyone because of the difficulty level, but I have done it for various customers. Neck Ring, steel to aluminum.jpg
__________________
Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
#7
|
|||
|
|||
I don't think they are talking about the same thing as Kerry copyed and re-posted. They are saying they can't open the first two links in Kent's text part of his post. Think they were done wrong when he posted them.
Attachment 41538 under WELDING, Attachment 41539 under SILVER - BRAZING They both take you to another page saying, "Invalid Attachment specified. If you followed a valid link, please notify the administrator"
__________________
The Rod Doctor, Richard Crees Last edited by TheRodDoc; 05-01-2017 at 11:19 AM. |
#8
|
||||
|
||||
OK, Kent sent me the two photos and I inserted them in the original post. I hope everyone can see them. I can.
__________________
Kerry Pinkerton |
#9
|
|||
|
|||
Quote:
Kerry, Thumbs are now Up. Thank you,
__________________
Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
#10
|
||||
|
||||
I see them now! Thanks Kerry.
Steve
__________________
Steve Hamilton Hamilton Classics Auto Restoration & Metalshaping |
Thread Tools | Search this Thread |
Display Modes | |
|
|