Brazing aluminum?

[ScotY]

I need to modify some aluminum tube for my a/c system and am wondering how hard it is to braze aluminum.  I've seen a few different miracle products that make it look VERY easy.  I'm talking about the kind of stuff you probably have seen on infomercials...expensive, no flux, all you do is clean with a stainless steel brush and braze away with a regular old propane torch. 

Do these products work?  What would be the best thing to buy from a real welding supply shop for the job?

Thanks, Scot

[ScotY]

Anyone?  Hey, I don't have a TIG so I gotta go on the cheap!   I bought some of this stuff from the local Gaspro.  No one there had any idea if it works or not. 
http://www.aladdin3in1.com/whitemetal.htm

[catfishblues]

I've only heard of somebody using the fluxed aluminum "soldering" rods from HF once. Filling some holes in an aluminum truck toolbox. Seems like it worked pretty well for him. Try those and tell us how it goes. Sorry! I don't think any of us have any better input.

[durnzuki]

The propane doesnt do a good job of brazing it, but you can buy a hotter gas, the name escapes me at the moment, that does a good job.  I have repaired aluminum radiators with it and they still dont leak.

[Freebird01]

MAPP gas...you can get it at any hardware store or home center works better then propane

[durnzuki]

THANK YOU Freebird!!  That is what I was talking about,  my brain is working slower than usual this morning.

[Freebird01]

THANK YOU Freebird!!  That is what I was talking about,  my brain is working slower than usual this morning.

guess i did my good deed by helping the elderly today HAHAHAHAHA

[ScotY]

But, hey, they make it look easy on TV!   I'll give it a try and see just how easy (or not) it is. 

I'm thinking I bought the wrong stuff though.  The rod I got has no flux, you're suppossed to heat and wirebrush to clean the oxidation.  Since I want to weld aluminum tube, I think I'm going to need to get something with a flux since I can't clean the inside of the tube.  I'm trying to join two pieces of tube, not sure what kind of joint that's called, but basically one tube inside the other.

[Whitfield]

I'd scuff it with some 80 grit and a rat tail file JB weld and let it go...  I've had enough brazing to last me this year.

That state fair / infomercial stuff takes time / skill to master.  We tried some at work 10 yrs back with so so results / Not good engouh to try again.

What AC line are you working with?  Custom application ~

I think I've still got a few useable OEM lines.

[azdesertrhino]

Brazing aluminum is very touchy. Along with a good product, I know you are supposed to use a stainless steel brush that has not been used on other metals.

Below is a link that should give some good information.


http://www.aws.org/wj/2004/02/046/

[Sarge]

The whole problem with aluminum is the coating of electrolysis, the stuff has a much higher melting point than the base metal itself . To properly prepare aluminum you must use a clean stainless steel brush that has never been used on any carbon-based metal (ferrous). The surface will need to be very clean and shiny , no contamination allowed or the weld will not be strong and pit-free . Any black pepper-like material coming up into the puddle indicates contamination. A good hot torch and a stainless brush along with some elbow grease goes a long way. Flux-type soldering filler is good but don't expect tig-like results here . Using a good clean low temperature filler rod along with a lot of cleaning is the way to go. If it's for any serious pressure lines, forget it as that type of rod will not have enough strength . Also, there are nearly 11,000 varieties of aluminum including the cast varieties. Attempting to join two dissimliar types will result in failure since certain types melt at very different rates and temps. Most AC lines are in the 3000-6000 series aluminum but some are the nearly impossible to weld 7000, you'll find out when you melt it as it will fall apart . Most good fillers are 5056 and 5063, they seem to work with nearly anything. Biggest trick is to keep it clean and apply heat quickly and smooth to keep the puddle under control. Take too much time and your work turns to goo....

Sarge

[ScotY]

What AC line are you working with?  Custom application ~

I think I've still got a few useable OEM lines.

Hey Whitfield,
Sent a PM to you re. your OEM lines.

[ScotY]

I did read about using a stainless steel brush and cleaning well.  Problem is cleaning the inside of the tube in order to join it to the smaller one, slip fit type deal.  I assume I should use a flux type brazing rod which I didn't buy.  I'll go back to the welding supply shop and see what they have.

I'm wanting to join two aluminum tubes for my a/c system.  I'd say the max. pressure would normally be a little over 200 psi, maybe a little higher but shouldn't exceed 300 psi.  I have a damaged tube that I'm trying to repair and it would be better to get a good condition used piece but they seem hard to find and new isn't an option as it's discontinued by Suzuki.  Another problem is the part I need uses an odd size fitting that is hard to match up.  Ideally, I could find a used replacement part then braze my fitting on to that.