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Welding aluminium and silver


#1

Hi everyone, I have a design job to do which involves connecting
aluminium to silver for a very large piece. I have been thinking
threaded connections, but was wondering if it is possible to weld
these two together? I don’t think this is possible, but someone else
might know differently. Any suggestions, ideas?

TIA, Christine in S.A.


#2
I have a design job to do which involves connecting aluminium to
silver for a very large piece. I have been thinking threaded
connections, but was wondering if it is possible to weld these two
together? I don't think this is possible, but someone else might
know differently. Any suggestions, ideas? 

It’s going to have to be some form of cold connection, either
adhesive or mechanical or both. In theory one can attach aluminum
to other non-ferrous metal with some specific soft solders and flux
combinations, but it isn’t worth the headache.

Even with the mechanical connection, I wouldn’t be surprised if you
have electrolytic corrosion issues between the silver and aluminum.

Ron Charlotte – Gainesville, FL


#3

Hi Christine,

I assume from your signature SA that you live is South Africa? If so,
then Afrox SA make an Aluminium Brazing flux (ref. No. 001/753) and
the matching brazing rods to braze (not weld) aluminium. It is a bit
tricky to use, since the parent metal, (in your case silver) has to
be brought up to just before the melting temperature of the
aluminium.

However, I have successfully brazed the two together before.The
joint is very brittle and suffers very little rolling or bending.The
thicker the metal the easier control is with a reducing flame.
Brazing
aluminium is not easy. It has a tendency to collapse suddenly,
ruining the piece because it does not ‘glow’ a visible temperature in
normal light.One way to overcome this is to make your flame ‘sooty’.

To explain: You align your joints and flux with the aluminium flux
mixed with water. Then you make you flame sooty and blacken the area
to be soldered. Then, with a reducing flame, you start heating up the
soldering area until the sootyness starts to disappear. Now you are
close to soldering temperature This allows you to ‘see’ how the two
different metals are heating up.It takes a bit of practice but I
have done it successfully on 200mm (bangle) pieces before. Aluminium
absorbs heat readily and collapses long before silver and so care is
needed.

Also, I roll the rod out and cut small pieces to put on the joint.
Then blacken and braze.

And lastly, if you want to aneal aluminium, then blackening it with
your flame is a good ‘temperature’ control as to how far to go. That
is, when the soot disappears it is time to stop. Soldering
temperature is just beyond that.

When you speak of threaded pieces, I think you might be involved in
larger work than brazing is feasible.(maybe) But up to 500mm I don’t
see too much of a problem with the right torch and flame control. I
use Oxy/Propane as my heat source. I am welcome to any questions.

Cheers, Hans Meevis.
http://www.meevis.com


#4

thank you Hans and Ron for your replies and help. This is one of
those headache type jobs, but very exciting with it, and I really
want to do this. I ( along with only two others) have been asked to
tender for design and manufacture of this object, and i think i will
recommend Titanium and silver for durability, and use all cold
connections.

I will practise brazing of Aluminium ( thank hans), for other
smaller jobs in the future, thanks again, all info is greatly
appreciated, Christine in Sth Australia :slight_smile: