Soldering or brazing aluminium help

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stragenmitsuko

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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 .





 

Nick Hulme

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Get a tube flaring kit or have it done professionally.
 

kiwi2

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

stragenmitsuko

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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 .
 

stragenmitsuko

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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 .
IMG-20190613-00001.jpg
 
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stragenmitsuko

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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 .

IMG-20190613-00002.jpg
IMG-20190613-00003.jpg
IMG-20190613-00004.jpg
IMG-20190613-00005.jpg
 
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stragenmitsuko

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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 !
 

deeferdog

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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.
 

bazmak

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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
 

goldstar31

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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
 

stragenmitsuko

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

Neil Lickfold

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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
 

Jennifer Edwards

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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

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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.
 

stragenmitsuko

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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 .
 

Jennifer Edwards

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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

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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
 

Jennifer Edwards

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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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