# Soldering or brazing aluminium help



## stragenmitsuko (Jun 2, 2019)

Guys , I 'm call on this list's wisdom . 

I need to solder or braze an aluminium AC condensor . 
The person who removed it couldn't undo the nut at the condensor side , and decided 
to twist it until it broke off ..... at both ends . 

The tube wall thickness is 1mm ( 1/32") , and altough I consider myself a reasonable tig welder , I think this is impossible to weld . 

These kind of repairs call for a capillary  joint . But on aluminium  that is not an easy task .
I know it's possible , I ve seen it more then once on alu AC systems . 

Anyone have experiance with this . 
There are fluxes out there that ought to work , but I haven't been able to  find any . I'm in Europe btw . 
I know about these brazing rods where you have to scratch the molten joint with a tungsten needle  , but that won't work here  I'm afraid . 

Tubing is 12mm od , with a 1mm wall , the repair is 12mm id with a wall of 2mm . 

Suggestions , comments ... fire away . 



Picture of the broken part , and the repair part  I made .


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## Nick Hulme (Jun 2, 2019)

Get a tube flaring kit or have it done professionally.


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## kiwi2 (Jun 3, 2019)

What about trying a swagelock connector. I believe they are gas tight.
Regards,
Alan


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## stragenmitsuko (Jun 3, 2019)

I have flaring tools , but that doesn't work on thin walled alu tube . 
It'll work , but won't last long , especially in a car . 

Swagelock's won't work either , the material is to soft for that . 

Soldering or brazing is the only way .


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## Ghosty (Jun 5, 2019)

Seen this add on facebook, know nothing about it, had something similar in the 80's
https://bonxashop.com/products/easy...CWRYcINWDLkN58c3YInKkE9YEfOMREtT2ipHI5WEfixiY

Looks like it would work.
Cheers
Andrew


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## stragenmitsuko (Jun 13, 2019)

Guys , what can I say ... I'm speechless .
Friend of mine  who's an hvac technician gave me 5 rods .
He said he bought it years ago , tried it and couldn't get it to work . 

So this evening I reluctantly did some test pieces , using an acetylene / oxygen 
torch as a heat source . Expecting nothing good really but couldn't hurt to try either . 

The first test was a disaster because I applied way to much heat .
The aluminium doesn't give a warning when it's up to temperature . And when itturns dull grey it's to late .


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## stragenmitsuko (Jun 13, 2019)

So the next 3 test pieces  I turned down the oxygene just to the point where  the flame goes  from blue to yellow . And then back a bit , a  tiny little bit on the blue side otherwise I wouldn't see anything .

And then like magic .... look at the pictures .


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## stragenmitsuko (Jun 13, 2019)

I cut the last one in half to see if it was fully joined . 
It was . I tried to polish it a bit , it's hard to see in the foto . 
There is the large piece , the thin walled tubing and a very fine line between them wich is the jointing material . 
The other half , I tried pulling it apart with a vice grips . The thin walled tubing sheared off , but the joined material didn't give way . 

This stuff flows like silver solder on copper or even better . 

The brand is castolin , the part nr is 192CW . 
It's a rod with integrated flux , no additional flux needed . 
They have a representation in Belgium so It shouldn't be to hard to find a supplier . 

Will keep you all posted !


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## deeferdog (Jun 13, 2019)

Years ago, when I was taught fusion welding of aluminium using oxy-acetylene, we would light the torch on acetylene only and coat the workpiece with the soot from the flame, then using a slightly carburising flame, heat the workpiece until the black soot just disappears. The job was then at the perfect welding temp. Years since I've done it but it should still work. Cheers, Peter.


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## bazmak (Jun 13, 2019)

Anybody tried the new sintered rods that are being heavily advertised at the moment
for alum and zinc based metals.They certainly seem the bees knees but not cheap


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## goldstar31 (Jun 14, 2019)

Hi Barry

I bought a few Durafix rods from Chronos in the UK. It was to join a broken bracket on a Myford ML10.

Whether the broken metal was aluminium or duralumin or whatever, I was unsuccessful 
Maybe me, maybe my tooling but the joint broke each time.
I would think that it would be possible to mould small items, if I wanted them.
The Durafix instructions suggest scratching the join and I had a stainless little dental brush( ex my late wife's kit). 

OK, I was a Certified welder from the days of being a manure student and can still happily silver solder and arc, lead load and Mig weld.  No use with this stuff.

There are people who can weld or solder some things and not others, not just me.
There is a knack but I haven't got it

Cheers

Norm


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## stragenmitsuko (Jun 14, 2019)

Yes , I've also tried those "scratching" rods . With exactly thesame results . 
Doesnt't work , or at least I cant get them to work .


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## JimDobson (Jun 14, 2019)

I've never had much luck with the ali rods that you can buy from the hardware and use LPG gas (supposedly) one them.


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## Neil Lickfold (Jun 14, 2019)

I use a propane torch and Harris Al Braze 1070 https://www.harrisproductsgroup.com/en/Products/Alloys/Brazing/Aluminum/AL-Braze-1070.aspx
The brazing rod I use is 4032 in 1mm wire, or you can buy Al brazing rod,and is very similar to 4032. The albraze flux is great. Clean the parts really clean, and degrease. Then apply the 1070 flux.  When it turns to water, add the rod filler and it will just flow. When it is water , you are only 15F or so from melting the 6061 or what ever alloy you are brazing. You can't braze the 4032, unless you have a eutectic brazing alloy, and will need a lower temp flux.  Propane or LPG works really well. I found acetylene to be too dirty and too intense a heat. I know people that do use the acetylene air torches too.
I like the fluffy flame style. 
Neil


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## Jennifer Edwards (Jun 14, 2019)

Stragenmitsuko,

What I use for very thin aluminium tubing and repairing other tiny metal parts that I am afraid will melt is simply “soft” 9 carat white gold solder. Yellow is ok too I just use white to blend in with my work.

Higher carat gold has too high a melting point so stick with the cheap stuff. It makes a very strong joint and will never corrode.

Use the smallest flame possible ( I have a jewellers oxy/acetylene torch that works great for fine work), and a neutral flame.

Just warm up the piece a bit, sprinkle some borax (flux) on it then with tweezers place a few tiny chips of the gold solder on the joint and slowly heat it, taking your time. You will see the solder just instantly flow when it hits its temp. IMMEDIATELY back off the flame. That’s all there is to it.

You can also buy the solder in paste form that had flux built in, but it costs about £10 more than just the solder alone. Also I find it easier to see the chips flow than to tell when the paste has melted.

Now this is where care and patience in heating comes into play. The difference between the solder flowing and the aluminium melting is only fifty five degrees Celsius 605  vs 660 for pure aluminium.

Just use the smallest flame possible, keep it moving, and keep it as far away as possible from your work but still heats it up.

I promise with a little practice you will get the hang of it and be easily soldering the stuff like a professional in no time.

 I believe the alloys used for HVAC tubing melts a little higher than pure aluminium, but cannot swear to it, maybe someone on the forum knows?

I know you are saying ARRRGGGGHHH GOLD... spenny!

It is really not that expensive. Jewellery supply companies sells the stuff pre cut into tiny chips by the penny weight, some companies by the gram. You can buy a single pennyweight if you wish. Prices are usually about 10% or so above “spot”price.

A gram is enough to make twenty or thirty joints like yours. I found a pennyweight for sale on the net today for £34 delivered.

Jenny


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## Murph (Jun 14, 2019)

I've worked with those rods, and the big points are to watch your heat - you're working with a very narrow window to make these work. Propane/air works a treat, acetylene/air - not as well, gets too hot, too fast!

The other thing is to use a clean stainless steel brush, if it's contaminated, you're knackered before you even start.

There are several different rods, solid, flux cored, separate flux, and no-flux. Some of these rods are aluminium/zinc alloys, make sure what you're using is up to the job at hand.


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## stragenmitsuko (Jun 14, 2019)

So true , a very small flame and patience is the way  to go .
I did use an oxy/acet torch , with the smallest tip I had , and a very small flame .
And even then one of my test pieces just melted . I forgot to keep the flame moving while
I was adding solder . Its just that I don't have a decent propane torch .

As an indicator of temperature , I put a small blob of solder on the part , and then start to heat
it slowly and evenly .  As soon as the blob starts to react  it is time to add a little more  rod .
Doesn't need much as it's a capillary joint .
Yesterday , I saw a video by tom lipton , and he said , the trick is knowing when to stop .
You can always add a little more , but when it's done it's done . Back off and leave it to cool down .

Anyway , I had 5 parts to repair , and four of them went very good .
The fifth one was badly corroded , and altough I cleaned it as good as possible  with
scotchbrite ,there was considerable pitting and  the solder just wouldn't catch .
Tomorrow I'll get me a piece of 12mm tubing and replace the entire corroded section .

Thx for all the good advices . I'm sure I'll be doing more of this kind of joints in the future .


@Jenny , I've never even heard of goldsolder . Sounds interesting for sure  .
Altough my first reaction was indeed gold ?? as in $$$$ gold ....

I'll make some more pictures when the 5'th section is also done .


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## Jennifer Edwards (Jun 14, 2019)

yes it really is about your touch. it really makes little difference what type of fuel you use. If you do not do it on a regular basis you will have to suffer the occasional mess up.

when i was knocking around southern California i had the good fortune to apprentice for a year or so for an old time bench jeweler, where I learned  to keep metals like silver and gold right on that temp where plus a few degrees would have the piece puddle and a few too cool and it was hard. mostly for re-pronging cocktail rings, or studs.

After that i went to work for a high end aluminum yacht builder. we made boats no less han 105 feet long. i must have laid a thousand mies of aluminum bead with a mig welder durng the two and a half years I worked there.

I like the oxy/acet jewelers torch because it has a pinpoint flame. I can adjus the flame sizet a little larger or smaller as needed for controlling the QUANTITY of heat i require, and simply vary the distance of the flame to control the TEMPERATURE of my target. If you think of it in those terms it becomes simple.

the gold solder trick works very well, and low carat gold is quite tough stuff.

It comes in three types, what jewelers call soft, medium and hard which has nothing to do with the hardness of the metal. in fact the hard solder is actually a bit softer because of the alloys they use.

Rather they are referring to the melting temp, soft being the lowest. they make it that way so you can say size a ring with "Hard" solder, then attach a finding to the ring shank with a solft solder withut melting the joint you made sizing the ring. Or you can do just the opposite, use hard to attach the finding and soft to size the piece without the finding falling off. You get the idea.

any way just my two cents


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## goody (Jun 14, 2019)

I have gas welded aluminum, long time ago.    The secret I was taught was to use goggles with a blue lens, the blue let’s you see the puddle, and you have to work fast.    I have been successful using a butane air torch on small parts with aluminum solder.    Will have to try the low alloy gold solder.  

Pat


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## Jennifer Edwards (Jun 15, 2019)

goody said:


> I have gas welded aluminum, long time ago.    The secret I was taught was to use goggles with a blue lens, the blue let’s you see the puddle, and you have to work fast.    I have been successful using a butane air torch on small parts with aluminum solder.    Will have to try the low alloy gold solder.
> 
> Pat



Hi Pat,

The blue lens may be the trick, Aluminium does glow a real faint orange before melting down. It is super difficult to see with the light from a flame in the way.

Jenny


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## XD351 (Jun 15, 2019)

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 .


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## Murph (Jun 15, 2019)

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!!!!!


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## Bazzer (Jun 15, 2019)

*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


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## JeffersonHouse (Jun 16, 2019)

*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?


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## stragenmitsuko (Jun 16, 2019)

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 .


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## WOB (Jun 17, 2019)

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


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## Preston Engebretson (Jun 18, 2019)

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


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## stragenmitsuko (Jun 19, 2019)

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


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## Shopgeezer (Jun 19, 2019)

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.


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## stragenmitsuko (Jun 19, 2019)

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 .


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## TSutrina (Jun 20, 2019)

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.


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## Shopgeezer (Jun 20, 2019)

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

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


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## cephas (Jul 1, 2019)

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


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## goldstar31 (Jul 2, 2019)

Joe

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

Regards

Norman


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