[Jewelry making - Article 00666] - Re: [Orchid] Welding aluminium and silver

[hans]

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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
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