Author Topic: Appx wattage needed for solding aluminum tubing with soldering iron?  (Read 3578 times)

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Offline pipe2null

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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
 

Online Fraser

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #1 on: June 24, 2022, 03:51:28 pm »
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
 
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Online Fraser

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Online mag_therm

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #3 on: June 24, 2022, 04:06:32 pm »
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
 
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Offline pipe2null

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #4 on: June 25, 2022, 02:05:50 am »
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!
 

Offline wizard69

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #5 on: June 25, 2022, 07:12:54 am »
Sadly I'm going to have to say that most soldering irons will not even come close.   Not know the specifics of this joint I do have a suggestion worth looking into, and that would be inductive bolt heaters.   You could also look into induction heaters specifically for this usage: https://ultraflexpower.com/induction-products/?campaign=853295958&adgroup=44243703555&keyword=induction%20heating%20equipment&creative=216812048600&gclid=EAIaIQobChMI4-LQwYHI-AIVtTizAB33GQY1EAAYASAAEgLhAfD_BwE.   The induciton bolt heaters are like these: https://www.amazon.com/s?k=heat+induction+bolt+remover&gclid=EAIaIQobChMI4-LQwYHI-AIVtTizAB33GQY1EAAYAyAAEgIjS_D_BwE&hvadid=521278154588&hvdev=c&hvlocphy=9067609&hvnetw=g&hvqmt=e&hvrand=3195435156427248570&hvtargid=kwd-915459744187&hydadcr=29041_10165998&tag=googhydr-20&ref=pd_sl_8t27f3xahf_e which gives you 1000 watts of power.   I only mention these units because the dimensions mentioned might allow for success.   If you are dealing with closed circuits then you might have to become creative with the induction loop.   I'm sure if you look around a bit you will find more of these and similar designs for brazing tubing.

As for the issue of joint being pulled apart when moving to a different side, my suggestion is don't!   come up with a system that heats up the entire perimeter all at once and melts the braze filler into the joint all at once.   One of the advantages of induction heating is that you can heat an entire diameter evenly.   With the joint prepped with flux and a snip of wire wrapped around the entire joint, getting good flow of the braze material should be easy.   Done right the braze materiel should all flow into the joint at the same time.

Given all of that it might be easier just to go out and buy another gas bottle for the torch you have.   If you need more back ground this might help: https://www.efd-induction.com/en/induction-heating-applications, maybe a bit too high end but good info.   I actually believe that inductions systems are now avaiable for plumbers and pipe fitters to do braze or soldered joints.    At least I seen such advertised at one time.
 
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Online mag_therm

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #6 on: June 25, 2022, 05:10:54 pm »
I am using Forney 46111 rods which seem the same as Harbor freight "Alumiweld"
387 C 730 F
There is very little mushy zone and the melt flows like , say, milk.

The joints have to be nearly horizontal. 20 degrees off and the braze would run away.

The "close joint" problem means that only one side of a braze can be done.
Both side of an inverted T joint can be done if the base is horizontal.

If trying to do a double bevel butt joint, when turning it over to fill the other side, the first side just runs away.

To prepare a butt joint then, it means that a single bevel is made and then filled up from one side.
But that leaves a stress concentration on the other side.

Also, to get a good joint, the surfaces under melt have to be stirred or "scarified" to release flakes of oxide which end up as a dull finish on top of the braze.
(a shiny finish might mean a bad joint)
 I find that trying to use the rod to do that, results in too much filler,
because , of course the rod continues to melt. So I use a sharpened tool steel held in the vice grips to stir.
The parts have to be solidly clamped otherwise they will move during the stirring.

Those issues, and the metallurgical problems described in following paper
mean that (for my usage and methods) this type of Al brazing is only useful for low stress jobs , like non critical electronics hardware etc.
search: "Dai_et_al_Microstructure_and_Properties_of_6061_Aluminum_Alloy_Brazing_Joint_with_Al–Si–Zn_Filler_Metal_en.pdf"
« Last Edit: June 25, 2022, 06:06:28 pm by mag_therm »
 

Offline Doctorandus_P

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #7 on: June 25, 2022, 05:33:02 pm »
One of the problems with trying to work with an iron is to get the heat transfered form the tip to the aluminium, and I doubt it's going to work.

What you could try is to put some wet rags on (or behind) those other joints to cool them down enough so the solder won't melt again. Thiw sill create big temperature gradients and thus you will need a bigger flame to compensate for that.

Yet another option is to make a jig that holds all the parts in place, then solder the joints and take it out of the jig after cooling.

Another option is to use a smaller but hotter flame to put more localized heat right at the right spots.
 

Offline BrokenYugo

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #8 on: June 25, 2022, 06:44:54 pm »
The electric tool for this job is a TIG welder, not a soldering iron.

If you can't see the puddle, get a good enough adjustable auto darkening helmet (sensors above and below viewing window, user serviceable battery) so you can. Biggest thing about learning to weld well is to see what you're doing, if you can't see the puddle, metal it is or is not wetting on, crack you're following, etc. you can't make corrections on the fly.

Those brazing rods are handy, but they're only so useful.
 

Offline langwadt

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #9 on: June 25, 2022, 06:49:53 pm »
The electric tool for this job is a TIG welder, not a soldering iron.

If you can't see the puddle, get a good enough adjustable auto darkening helmet (sensors above and below viewing window, user serviceable battery) so you can. Biggest thing about learning to weld well is to see what you're doing, if you can't see the puddle, metal it is or is not wetting on, crack you're following, etc. you can't make corrections on the fly.

Those brazing rods are handy, but they're only so useful.

needs to be AC TIG and not all types of aluminium can be welded

 

Offline pipe2null

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #10 on: June 25, 2022, 08:29:18 pm »
Thanks for all the feedback.

Looks like I am officially in the market for my first TIG machine to tack joints together and refilling my tanks to use my existing mini jewelers mixed gas torch (Smith's "Little Torch") to braze joints to get water-tight-ness.  My thought is that as long as the joints are tacked together with TIG (solid up to 660 degC), soldering many joints should not be an issue since even if solder in previous joints re-melt when the whole part goes above 450 degC, surface tension will hold molten solder in the joint as long as the pieces are immobilized by the TIG tack welds.  Obviously, it would be better if my TIG skill were good enough just to weld the whole piece, but that's nowhere near realistic yet.


Currently diving into the many variations of welding machines that include TIG.
 

Offline Marco

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #11 on: June 25, 2022, 08:40:44 pm »
Can't TIG welding work pulsed too BTW? Basically doing overlapping spot welds which don't heat up much of the material.

This doesn't seem to generate much heat in the workpiece :
https://www.youtube.com/watch?v=_3IwnplHltg&t=530s
« Last Edit: June 25, 2022, 09:32:15 pm by Marco »
 

Offline langwadt

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #12 on: June 25, 2022, 11:21:35 pm »
Can't TIG welding work pulsed too BTW? Basically doing overlapping spot welds which don't heat up much of the material.

This doesn't seem to generate much heat in the workpiece :
https://www.youtube.com/watch?v=_3IwnplHltg&t=530s

https://youtu.be/V7-mcjR59a4 ...
 

Offline Marco

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #13 on: June 26, 2022, 02:49:31 am »
It only needed to be water tight, not structurally sound.
 

Offline Ground_Loop

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #14 on: June 26, 2022, 03:10:13 am »
You might want to check out irons used for stained glass such as Weller W100P or 1175.
There's no point getting old if you don't have stories.
 

Offline pipe2null

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #15 on: June 28, 2022, 10:52:57 pm »
I'm curious about the so-called "Cold Weld" mode, although as The Fabrication Series points out, it is just a psuedo pulsed tack weld mode that goes full off between pulses, and "Cold Weld" is literally a welding defect due to really poor penetration usually referred to as a cold weld. 

I still would not trust overlapping tack welds to be water tight, but I am curious how to simulate that "Cold Weld" mode with a real TIG welding machine... Might still be useful for me until I get my TIG skill good enough and still rely on brazing for water tightness.  Do you just unplug the pedal and tape a clicker to the torch?  Is it still using Argon at normal flow?


Any recommendations on web forums for buyer's advice for TIG/multi-process welding machines?  There's always people on Eevblog for any subject you can think of, but I hesitate to ask general questions here that are as far removed from electronics as multi-process welding machine purchase advice.
 

Offline Someone

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #16 on: June 28, 2022, 11:19:11 pm »
If the object can withstand some heat, why bother with a high-skill method like welding? Adhesives such as Permabond ES558 can be cheaper, or marine silicone....
 

Offline BrokenYugo

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #17 on: June 29, 2022, 01:04:15 am »
IIRC it is pretty typical for modern inverter TIG machines to offer at least some waveform shaping options, check the manual.
 

Offline pipe2null

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #18 on: June 29, 2022, 01:47:23 am »
I did some early prototype parts using JB weld.  Most of the parts ended up working out ok, BUT: One prototype appeared to have good, fully cured joints.  I pressurized the part with an air compressor, submerged it, and it passed the test with no bubbles.  I ran it with coolant for a couple days without any power applied to the electronics, no problem.  2 days after I started using the JB welded part with power applied to the electronics, the bloody thing developed a small leak and literally fried a dual CPU server motherboard, complete with slag surrounding the VRM that blew up as result of the puddle.  Fortunately both CPU's and the RAM survived, but it was a hard lesson to learn, so, no more JB Weld type compounds for doing these joints.  Thus my transition to brazing and now adding TIG variations to my fabrication skill set.  Theoretically the same problem could occur with TIG-tacked and brazed joints, but my confidence level is much higher with an all metal joint that passes the same pressurized air submersion test for water-tightness.

Plus, I must admit that part of my desire to go the TIG route is simply that I've wanted to buy welding equipment to add to my shop for a while, but lacked sufficient justification for the purchase.  Still, for this project a nice and simple solution would be preferable, but it seems the TIG route would get the most reliable result with equipment purchases that are more general purpose, general use welding equipement compared to something more specialized with little use for me other than this specific project.
 

Online mag_therm

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #19 on: June 29, 2022, 07:41:04 pm »
Sorry to hear about that disaster.
Are you aware that thin wall copper tubing is available?  Copper greatly eases the difficulty of joining Aluminum and also has  corrosion resistance  with water.

Thin and thick wall rectangular copper tube is  used for high pressure water cooled coils and conductors in induction heating.
 
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Offline BrokenYugo

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #20 on: June 29, 2022, 10:41:21 pm »
A good point, if we're just doing typical computer water cooling then soft soldered copper is certainly an option, more costly material, but higher performance and easier/cheaper to work with.
 
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Offline Old Goat

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #21 on: June 30, 2022, 12:47:50 pm »
Thanks for all the feedback.
...

Currently diving into the many variations of welding machines that include TIG.

Take a look at Kevin Caron on youtube. He's a metal artist, and offers reviews of various TIG welders as well as many tips and procedures for welding various materials.
Don't Ever Say Never
 
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Offline wizard69

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #22 on: July 03, 2022, 08:22:58 pm »
If that is what you are doing I'd have to say STOP.   If aluminum tubing and brazing was a reasonable solution for any plumbing need we would be seeing more of it in use.   There are some systems for airlines out there that use aluminum successfully but they also leverage compression fittings.

I've seen a lot of these computer chilling systems over the years and have to wonder why they don't use common industrial solutions that are known to work well.   Swagelok is one approach and there are all sorts of plumbing type components for refrigeration systems.   Swagelok is frankly pretty easy to use and can interface to stainless, copper and a variety of plastic hoses.   

If you go with copper there are so many reliable ways to make up connections that there is almost always a reliable commercial solution available.   That could be soldered or brazed connections or some sort of compression fitting.
I did some early prototype parts using JB weld.  Most of the parts ended up working out ok, BUT: One prototype appeared to have good, fully cured joints.  I pressurized the part with an air compressor, submerged it, and it passed the test with no bubbles.  I ran it with coolant for a couple days without any power applied to the electronics, no problem.  2 days after I started using the JB welded part with power applied to the electronics, the bloody thing developed a small leak and literally fried a dual CPU server motherboard, complete with slag surrounding the VRM that blew up as result of the puddle.  Fortunately both CPU's and the RAM survived, but it was a hard lesson to learn, so, no more JB Weld type compounds for doing these joints.  Thus my transition to brazing and now adding TIG variations to my fabrication skill set.  Theoretically the same problem could occur with TIG-tacked and brazed joints, but my confidence level is much higher with an all metal joint that passes the same pressurized air submersion test for water-tightness.

Plus, I must admit that part of my desire to go the TIG route is simply that I've wanted to buy welding equipment to add to my shop for a while, but lacked sufficient justification for the purchase.  Still, for this project a nice and simple solution would be preferable, but it seems the TIG route would get the most reliable result with equipment purchases that are more general purpose, general use welding equipement compared to something more specialized with little use for me other than this specific project.
 

Offline langwadt

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #23 on: July 04, 2022, 07:05:34 am »
If that is what you are doing I'd have to say STOP.   If aluminum tubing and brazing was a reasonable solution for any plumbing need we would be seeing more of it in use.   There are some systems for airlines out there that use aluminum successfully but they also leverage compression fittings.

I've seen a lot of these computer chilling systems over the years and have to wonder why they don't use common industrial solutions that are known to work well.   Swagelok is one approach and there are all sorts of plumbing type components for refrigeration systems.   Swagelok is frankly pretty easy to use and can interface to stainless, copper and a variety of plastic hoses.   


yes swagelok is very nice, but also very expensive
 

Offline beanflying

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Re: Appx wattage needed for solding aluminum tubing with soldering iron?
« Reply #24 on: July 04, 2022, 07:31:10 am »
Won't try and talk you out of a good Tig welder as I talked myself into one late last year  >:D

For Aluminium Brazing it's all about heat volume more than absolute temperature. Have a trawl through this repair I did a while ago on a badly broken Cast Ali frame. https://www.eevblog.com/forum/testgear/hewlett-packard-740b-dc-standard-digital-voltmeter-(and-740a)/msg1420035/#msg1420035
Coffee, Food, R/C and electronics nerd in no particular order. Also CNC wannabe, 3D printer and Laser Cutter Junkie and just don't mention my TEA addiction....
 


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