All MetalShaping

Go Back   All MetalShaping > General Metal Shaping Discussion > Welding Sheet Metal
  Today's Posts Posts for Last 7 Days Posts for Last 14 Days  

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 04-28-2017, 10:47 AM
crystallographic crystallographic is offline
MetalShaper of the Month October '14 , April '16, July 2020, Jan 2023
 
Join Date: Dec 2010
Location: Western Sierra Nevadas, Badger Hill, CA
Posts: 4,388
Default 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.
Reply With Quote
  #2  
Old 04-28-2017, 12:31 PM
longyard longyard is offline
MetalShaper of the Month September 2013
 
Join Date: May 2012
Location: Winston-Salem, NC
Posts: 1,083
Default

I always learn so much from you Kent. Thanks again for taking the time to teach this lesson.
__________________
Bill Longyard
Winston-Salem, NC
Reply With Quote
  #3  
Old 04-28-2017, 01:35 PM
cliffrod cliffrod is offline
MetalShaper of the Month January 2020, March 2022
 
Join Date: Dec 2014
Location: Spartanburg, SC
Posts: 2,845
Default

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
Reply With Quote
  #4  
Old 04-28-2017, 09:20 PM
crystallographic crystallographic is offline
MetalShaper of the Month October '14 , April '16, July 2020, Jan 2023
 
Join Date: Dec 2010
Location: Western Sierra Nevadas, Badger Hill, CA
Posts: 4,388
Default

Quote:
Originally Posted by cliffrod View Post
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.
Cliff,
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.
Reply With Quote
  #5  
Old 04-28-2017, 10:53 PM
BTromblay BTromblay is offline
ADMINISTRATOR MetalShaper of the Month August 2018
 
Join Date: Oct 2015
Location: Mukwonago, Wi
Posts: 567
Default

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.
Reply With Quote
  #6  
Old 04-29-2017, 12:05 AM
crystallographic crystallographic is offline
MetalShaper of the Month October '14 , April '16, July 2020, Jan 2023
 
Join Date: Dec 2010
Location: Western Sierra Nevadas, Badger Hill, CA
Posts: 4,388
Default

Quote:
Originally Posted by BTromblay View Post
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
Hi Bill,
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.
Reply With Quote
  #7  
Old 05-01-2017, 11:16 AM
TheRodDoc TheRodDoc is offline
MetalShaper of the Month Nov 2020
 
Join Date: Sep 2009
Location: iowa, USA
Posts: 446
Default

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.
Reply With Quote
  #8  
Old 05-01-2017, 06:04 PM
Kerry Pinkerton's Avatar
Kerry Pinkerton Kerry Pinkerton is offline
Administrator
 
Join Date: May 2009
Location: Near Huntsville, Alabama. Just south of the Tennessee line off I65
Posts: 8,321
Default

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
Reply With Quote
  #9  
Old 05-01-2017, 07:55 PM
crystallographic crystallographic is offline
MetalShaper of the Month October '14 , April '16, July 2020, Jan 2023
 
Join Date: Dec 2010
Location: Western Sierra Nevadas, Badger Hill, CA
Posts: 4,388
Default

Quote:
Originally Posted by Kerry Pinkerton View Post
OK, Kent sent me the two photos and I inserted them in the original post. I hope everyone can see them. I can.

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.
Reply With Quote
  #10  
Old 05-01-2017, 09:26 PM
Steve Hamilton's Avatar
Steve Hamilton Steve Hamilton is offline
ADMINISTRATOR MetalShaper of the Month Dec. '09 & May '11
 
Join Date: May 2009
Location: Fond du Lac WI.
Posts: 2,405
Default

I see them now! Thanks Kerry.
Steve
__________________
Steve Hamilton
Hamilton Classics
Auto Restoration & Metalshaping
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT -5. The time now is 05:35 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.