Soldering or brazing aluminium help

[XD351]

When i was taught to oxy weld aluminium we used to blacken the area with the soot from the acetylene as it burns off just before the aluminium melts .

 

[Murph]

Jenny, the friend who taught me to silver solder did jewelery work, he showed me how to set up the work, use alcohol to thin my flux - never water! He also showed me how to use India ink as a flow containment for silver soldering and brazing, using Liquid Paper to spread over solder joints as a stop flow while doing the next joint.

Years later, I taught him how to use milk of magenesia to control your solder spread, and listening to the pitch of the whistling on your acetylene/air TurboTorch (Swirlfire) tip to set your flame to the desired heat and size everytime!

Only place here in the US for the blue glasses is Rio Grande, jewelers love them for delicate work. AO Optical made them years ago for arc welding aluminium, but with the tint of the glass being done with cobalt salts, OSHA all but outlawed the making of the needed glass here in the US, IIRC. If you can find a Cool Blue lens, figure on paying $300-500 for it!!!!!

 

[Bazzer]

Soldering Aluminium

Aluminium solders like the best copper if it can be abraded and no oxygen is present, I have on occasions for very specific jobs soldered aluminium with normal solder and no flux as follows.

Create a puddle of solder around the tip of the iron, then abrade the aluminium but only in that puddle, then move on, I have managed to seem solder aluminium plates together like this.

I did experiment with modifing a tip on a soldering iron to look like a meat tenderising hammer, with this type of tip I was able to abrade the aluminium with the soldering iron, worked quite well.

When I was an apprentice many years ago, I remember an instructor saying that you cannot solder aluminium with normal solder, I said you can, he said prove it, so I soldered a piece of wire onto an aluminium plate.

The instructor said, right lad's this will just fall off the plate, he pulled on the wire so hard it pulled the wire out of the solder!!

Regards

Barrie

 

[JeffersonHouse]

Soldering Aluminium

I did experiment with modifing a tip on a soldering iron to look like a meat tenderising hammer, with this type of tip I was able to abrade the aluminium with the soldering iron, worked quite well. Barrie

Can you post a sketch? The method I get, but I can't visualize the soldering tip. How large of an iron are you using or can be used?

 

[stragenmitsuko]

When I was in highschool , wich is many years ago , we would experiment with oil or grease .
Cover the surface to be soldered , and then use sandpaper or scotchbrite to remove the oxide layer but keep the oil layer intact . The theory was that the grease or oil would shield the the surface from air , and thus prevent new oxydasiation .
Then it could be soldered with a powerfull soldering iron trough the oil layer . Once the surface was tinned , it could be wiped
and soldered normally .
Somtimes it worked , sometimes it didn't .

 

[WOB]

This company https://www.tinmantech.com/products...ion/TM2000-high-accuracy-gas-welding-lens.php
has been around for years and seem to have been one of the few selling lenses for gas welding and brazing aluminum. I have not used them, but I have always wondered about gas welding aluminum. Apparently, it was a common practice during WWII in aircraft production plants.

WOB

 

[Preston Engebretson]

Hola, I have used the Tinmantech lenses for gas welding aluminum for over 15 years...since first taking
Ron Fornells classes...the work wonderfully and allow one to see the puddle prefectly.

Best Regards,

Preston

 

[stragenmitsuko]

Job done !

I've had the entire system under 8bar pressure for 48hrs , with a gauge on it .
The gauge didn't drop a bit . So the repair was succesfull .

I had 3 8mm ( 3/8) pieces to solder .
They all soldered without a problem , and succeeded on the first attempt .


Here's a picture of an old one as an example , and a new one I made with a machined endpiece and stainless nut .
The stainless nuts are supposed to avoid the problem of the aluminium binding too the aluminium .
That is also the problem with the upper nut . There's no thread left in it .

But then I had a 12mm( 1/2) part to repair , directly on the condensor .
That would just not work . I ended up with either a blob of molten aluminium , or a joint that had pin holes in it , and was leaking . Ive tried this four times , and each time what was left of the condensor tube became a bit shorter .
No avail , either pinholes or a molten piece of crap . Re heating trying to melt the solder again and let if flow some more didn't work either . The part would just melt , the solder would not ! Tried both a propane torch and an oxy/ad torch .

So as t he condensor tubing got shorter and shorter , and my rods of solder also got down to the last one , I figured I needed to try something different . The product is advertised as being able to solder alu to copper .
So I made a repair piece out of copper/brass that I could silver solder . Then I flared the end of the copper to obtain some kind of funnel . And soldered those parts together .
That did the trick , altough the firsttime I also had pin holes , but reflowing it solved the problem .
The copper , with it's much higher melting point apparantly acts as a heat storage , and allows the solder to flow better without , or with less chance of overheating the aluminium .

So all in all it's been a great learning experiance , and I'm sure I will use this technique again if needed .

I've also ordered some flux , a liquid , that would allow soft soldering of aluminium .
Soft soldering won't work with the high pressures involved in cooling gasses , but there are plenty of applications
where it could be handy .

A quick word about my acetylene torch . When I started working , 30 years ago , at one of the major gas companies , there was a guy who was called the flame expert . A man close to his pension . He would go to customers and solve all kinds of welding and combustion problems . So I asked him can you recommend me a torch for small hobby use .
He replied by giving me and adress and said be there at around 8pm . It was his home adress , and when I got there he gave me a box with a torch . It was the best they ever made according to him , but it would last a lifetime so each indivudual only bought one . And so they ended production .
Take it he said , I'm sure you'll enjoy it and I don't need it anymore .
Bob , where ever you are now , know that I'm still using it and altough It's only once or twice a year , each time I do
I think of you for a moment . Cheers Pat

 

[Shopgeezer]

I wonder if the alloy you are using affects the brazing. Alloys such as 3003 and 6061 are weldable but others such as the common 2024 are not. It is always hard to tell what alloy your have in hand but if it just won't braze or solder it probably isn't a weldable alloy.

 

[stragenmitsuko]

That is quite possible .
All the materials I have is scrap metal salvaged from various machines .
And the 8mm ends ( the ones that did work ) were machined from a different piece of scrap .
I never thought of that , I'll do some testing .

 

[TSutrina]

I was making an aluminum compression bonded semiconductor switch with 7 one ton pressure force transistors an three compression diodes for about a 1000 ampere switch. The conductors and the tension members were 6061 T6 aluminum. The silicone in the aluminum made any soldering impossible and even plating was difficult. But we did find a vendor to silver plate the aluminum which then could hold solder to connect to the compression bonded terminals of the semiconductors. Basically the choice of aluminum is critical.

 

[Shopgeezer]

Aircraft Spruce has a good info page on the various aluminum alloys:

https://m.aircraftspruce.ca/catalog/mepages/aluminfo.php

 

[cephas]

Hello, stragenmitsuko,

What I have here would be my comment, not suggestion; but it could spawn some ideas, who knows. I had an occasion to solder a copper wire to aluminum plate by using a soldering gun. Wrap a strip of clean steel wool tightly around the gun tip, making it looking like a cotton swab. Place a piece of solder on the aluminum surface where the copper wire is to be soldered. Turn on the gun on full heat and scrub the solder bit on the area until it melts. When the solder melts, it displaces atmosphere air away from the aluminum surface and the steel wool soaked with molten solder makes available the reactive aluminum surface to take on solder. This is bypassing aluminum oxide interference. What you should have now is a "pre-tinned" spot on the aluminum plate. Hope this helps.
---Joe

 

[goldstar31]

Joe

From what I have read from UK manufacturers , steel wool is oiled.

Regards

Norman