Soldering Aluminium

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Soldering Aluminium

This topic has 9 replies, 7 voices, and was last updated 26 July 2024 at 11:37 by John MC.

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25 July 2024 at 16:21 #743498
John MC
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@johnmc39344
I am fitting a bush in to an aluminium casting, the bush will have an external thread in to the casting for mechanical security.

I thought it would be nice to run a bead of solder around the bush, mainly for appearance and back up oil tightness.

My usual go to for this would be something like Lumiweld or similar. Problem is the heat needed. There are components fitted near the bush that I do not want to disturb or get too hot, certainly not to Lumiweld temperatures.

My question is, is there such a thing as low temperature solder for aluminium. Something that can be used with a soldering iron? Mechanical strength is unimportant.

Any other ideas. I have tried things like “liquid metal” in the past. Did the job but not the same colour as the parent metal.

I’m open to suggestions, any ideas?
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25 July 2024 at 16:29 #743500
JasonB
Moderator
@jasonb
Alusol
25 July 2024 at 16:47 #743502
Andrew Tinsley
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@andrewtinsley63637
Jason has the correct answer! From memory you need about 200 degrees C to solder with Alusol. Last time I looked the stuff was an eyewatering £6 a metre from CUP or a few hundred gram reel from Farnell at £40 per reel. After paying through the nose to CUP, I purchased a reel from Farnell.

Andrew
25 July 2024 at 20:14 #743546
noel shelley
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@noelshelley55608
You will need the right flux I suspect ? Or is it cored ? Noel.
25 July 2024 at 20:22 #743549
JasonB
Moderator
@jasonb
Cored, saves the excessive postage on the separate flux.

I’m sure if anyone asked CuP they would do a good price for a reel ot large quantity as the other solders they list full reels of are a better buy than short bits plus you get all the advice from them included.
25 July 2024 at 20:48 #743553
Trevor Drabble 1
Participant
@trevordrabble1
The Solders and Flux company also sell Alusol. No connection with them other than as a satisfied customer.
26 July 2024 at 07:28 #743593
John MC
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@johnmc39344
Thanks for the replies. I’ll give cored Alusol a try. This still needs a some preheating of the work piece of the work before soldering, hopefully not too much. I’m hoping my large soldering iron will bring the heat up locally to do the job.

Also, I’ve noticed that these types of solder prefer pure aluminium, silicon is the enemy and it will not solder. One component is cast, the other wrought so there will be, likely, be some silicon present.

I’ve got two chances, I’ll give it a go and report back.

If it doesn’t work then plan B will be an epoxy type filler.
26 July 2024 at 09:51 #743607
bernard towers
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@bernardtowers37738
If the bits are large you could preheat with a hotter gun/hairdryer, it shoul d be a help.
26 July 2024 at 10:47 #743621
Hopper
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@hopper
On 25 July 2024 at 16:21 John MC Said:

.. I have tried things like “liquid metal” in the past. Did the job but not the same colour as the parent metal.

I’m open to suggestions, any ideas?

Can you make the theaded bushing a top-hat shape so the top-hat flange on the end obscures the threaded joint and any adhesive in it? You could even radius the outer edge of the flange and bead blast it so it looked like a casting.
26 July 2024 at 11:37 #743643
John MC
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@johnmc39344
The problem is that the bush passes through a casting that curves in all directions. If it was flat then it would be so much easier!
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