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Appx wattage needed for solding aluminum tubing with soldering iron?

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pipe2null:
I'm looking for a soldering iron with a high enough wattage and temperature to solder aluminum tube, simple square tubing 8mm x 8mm with 1mm walls.  The purpose of the soldering is to get air/water tight joints, but not under any significant pressure.

Some of the solder/brazing rods I've used melts around 440 degC, others is more into the 550 degC range.  Aluminum melts around 660 degC.  I've attempted using my little soldering station, but all the heat gets leached away from the joint I'm soldering, and the iron can't provide enough heat energy fast enough to get the joint up to temperature.  Previously I've used propane/mapp/oxy-propane torches to braze joints in aluminum tubing, but I'm out of gas at the moment so it's a good time to explore other options, preferably an all electric one.  As much as I like playing with fire, literally, maintaining tanks and a safe area to use them is a bit much when the sole purpose for the whole setup is to braze small aluminum parts.  I've considered getting a reflow heat plate to pre-heat the part, but that would still need a high enough wattage soldering iron to overcome the leaching, and I'd prefer to only need an iron (a single tool versus heat plate station plus tool versus tanks and torches and torch tips and.......).


Any advice on soldering these types of joints with a soldering iron?  Any idea what wattage is needed to overcome the heat leaching and still have a high enough temperature to get a good enough soldered joint?

Thanks

Fraser:
This article states 150W may be enough. I have only ever seen a gas torch used though. It will be the size of the workpiece and it’s ability to conduct the heat energy away from the joint that dictates whether an electric soldering iron is even feasible.

https://www.wikihow.com/Solder-Aluminum#:~:text=You%20can%20use%20a%20soldering,a%20150%20watt%20soldering%20iron.

Fraser

Fraser:
Useful article…

https://superiorflux.com/papers/TWJ.May.2018.Tech.Solder.Al.pdf

mag_therm:
The thermal conductivity of Al is so high that the whole object tends to rise to nearly the brazing temperature.
So the heat source has to be of sufficient power to do that with a bit left over to do the braze.
It might be possible to use a soldering iron rated for 400+ C if the object is placed on a heating pad that can hold it at about 360C.

I use oxy acet #1 tip - quite a lot of heating power for small jobs compared to steel.
 The brazed joints need some stirring of the melt to get the oxide to float out, necessitating rigid clamping that also sucks the heat away.

As an aside, I found that Al sections from the rack in the home hardware stores have some impurity that does not allow reliable brazed joints.

So now I only braze 6061 alloy sections purchased from metal suppliers.

I can braze moly bike tubing quite well, but this Al stuff is not easy for me!
https://app.box.com/s/7q6jydidh7e4p94tfgnece3sropneq46

pipe2null:
Great article on all the various methods for soldering Al.  And nice joints on that chassis (I swear I'm not being lewd).

The stock I'm using is at least advertised as Al 6063.  When I was previously using the oxy-propane torch I could get a decent braze on one joint, but the other joints were too close so when torching the second joint it would end up with enough heat leached back to the first joint to melt the solder and screw up the joint.  Which directed me into a rabbit hole of attempting to learn TIG welding of thin Al from youtube videos using a welding machine at my local Maker's Space, but then I got busy with life and the whole project got back burnered for a long while.  Some of my original prototype heat exchangers have been in daily use for over a year and a half without leaking and frying motherboards or GPUs (knock on wood).  I have extra time ATM, thought it was time to finally get the overall project done.

Thought it might be possible to take care of the problem of joints being too close plus eliminate the need for a torch by going all electric, but the fundamental heat conductivity problem looks to be unavoidable for tools within my price range.  I am curious about induction soldering, but that seems like it would be expensive.

Perhaps it's time to refill my tanks and then finally buy one of the TIG machines I've been drooling over for a long time.  Me tinks a few TIG tack welds plus brazing should get pretty decent very usable results, at least until my TIG skills evolve beyond burning holes in metal coupons.  (I jokingly refer to TIG welders as plasma cutters, but hopefully not for much longer.)

Thanks for the feedback!

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