Brazing aluminum ac line issues

[sean kidd]

All of the fittings I have are new beadlock crimp fittings...except the double horse shoe adapter at the compressor...which is rare at #12 suction
and #8 liquid (most are #10 and #8) the high pressure line had an integral crimp, not a ferrule, so I got a braze on beadlock fitting. For the life
of me I cannot get the aluminum to flow, and blew a hole in the side of the tube twice. Using map gas and blue demon triple play low temp 1/8 brazing
rods...I can sweat copper all day long but can't seam to get aluminum going...it's the last thing I need to finish for my double aux evaporators. Any
suggestions?
--
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.

Colonial Travelers

 

[a.]

> All of the fittings I have are new beadlock crimp fittings...except the double horse shoe adapter at the compressor...which is rare at #12
> suction and #8 liquid (most are #10 and #8) the high pressure line had an integral crimp, not a ferrule, so I got a braze on beadlock fitting. For
> the life of me I cannot get the aluminum to flow, and blew a hole in the side of the tube twice. Using map gas and blue demon triple play low temp
> 1/8 brazing rods...I can sweat copper all day long but can't seam to get aluminum going...it's the last thing I need to finish for my double aux
> evaporators. Any suggestions?

What kind of flux are you using?

 

[sean kidd]

Hot max powdered flux.
--
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.

Colonial Travelers

 

[a.]

> Hot max powdered flux.

Try a liquid or paste flux.

 

[Jim Hupy]

I prefer using a smaller diameter rod on that thin tubing. Make really sure
that it is squeaky clean. Watch the end of the rod and have it really close
to the tubing. When the ball on the end of the rod appears shiny, be ready
to push it into the weld affected zone (puddle) PRACTICE ON SOME SCRAP
FIRST.
JIM HUPY

> Hot max powdered flux.

Try a liquid or paste flux.

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[Matt Colie]

Sean,

In my experience, aluminum braze will never flow like a bronze on steel or other bronze. It can work it is just different.

I still (but rarely) weld aluminum with an oxy-acetylene torch (yeah, I'm that old) and with or without flux, the surface scale of aluminum is hard
(like aluminum oxide!). If you don't have that removed, it can screw up everything. I still keep stainless steel "tooth brushes" around for just this
purpose. With a TIG can at least give you a chance to break it up with the rod, but the force of the flame of any torch makes that a problem.

So, if you can get by a Hazard Fright, buy the set that includes stainless brushes.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[dave king]

Matt, I've never tried welding or "brazing" aluminum. I know a GREAT welder
so I don't "need" to know how to do it myself.
Isn't one of the problems with brazing/welding aluminum is that it doesn't change
color before it melts and sags away? Just what I've heard.
--
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada

 

[les burt]

My experience with brazing aluminum is that larger pieces can be a difficult problem. Small/thin stuff is easier, but only once you have figured out how to manage heat.

Heat management with TIG is easy compared to flame welding.

A few considerations for flame welding/brazing aluminum:
1- Aluminum is a good thermal conductor, quickly wicking the heat away from the weld zone, so a large piece needs to be thoroughly pre-heated to minimize this effect. Don't try to just heat the weld zone, as you will quickly learn it is harder to master, and requires a hotter flame.
2- Cleanliness of the weld zone is important.
3- if you have melted or blown out an area of the material, the surface is likely too dirty(oxidized) to be able to get the brazing to take hold. You need to stop, re-clean, and re-start your process.

I first learned how to braze aluminum by using the bottom of a soda can as practice material.
Cut a slit in the bottom, clean the surface, and try to fill the slit with the filler rod. The thin metal is easily overheated, so some finess is required. When you have mastered this, move on to tougher scrap materials for practice. I try not to practice on components that matter.

Les Burt
Montreal
'75 Eleganza 26'

>
> Matt, I've never tried welding or "brazing" aluminum. I know a GREAT welder
> so I don't "need" to know how to do it myself.
> Isn't one of the problems with brazing/welding aluminum is that it doesn't change
> color before it melts and sags away? Just what I've heard.
> --
> DAVE KING
> lurker, wannabe
> Toronto, Ontario, Canada
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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[Matt Colie]

> Matt, I've never tried welding or "brazing" aluminum. I know a GREAT welder
> so I don't "need" to know how to do it myself.
> Isn't one of the problems with brazing/welding aluminum is that it doesn't change
> color before it melts and sags away? Just what I've heard.

Dave,

Having an experienced welder available is (in most cases) better than knowing how to do it yourself.

As to the visible color change......
Oh you Fracking Bet You.
You have to start with a cobalt glass (blue) filter because the yellow flame of the flux is different. That is a good start to throwing you off your
comfort zone.
As I was first told by the wonderful person that taught me,"If the part goes liquid and runs off the bench, it was too hot."
This is a real bitch with aluminum because it is easy for it to have a surface scale of Al2O3 to hold it is shape when it is throughly molten. Then,
you hit is with the rod and the scale breaks....
(I don't think I need to tell you more about how I know all this.)

Matt



--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[RoadWarrior]

Old A/C lines are nearly impossible to braze or weld because of the Fluorine contamination from the refrigerant. Sometimes you can heat it gently and
dunk in distilled water several times to get the Fluorine out of the metal. Then mechanically clean, flux, and try again.

 

[john r. lebetski]

Would fitting Ts be a better idea? Before and after existing evaporator would make sense to me. Are such fittings available? I never understood how
you would weld into existing lines without heat ruining rubber and just being prone to leaks and cracks from vibration. And risk of slag internally.
--
John Lebetski
Woodstock, IL
77 Eleganza II