Peter Johns, if you're reading, can you tell us whether torch melting with flux to pour ingots for forging would be a problem for those of us who would like to work this way from casting grain?
James
Melting Argentium grain to cast small ingots with the torch should
not be a problem, as long as normal precautions are taken to prevent
oxidation. (I am assuming that you would be melting relatively small
amounts - less than 7oz).
In the UK, we use natural gas and compressed air torches and
therefore can set up the torch to produce a slightly reducing flame
to help protect the metal. This may be difficult with torches that
burn propane. I am also nervous about using very hot gases such as
oxyacetylene, as I believe these can burn the metal if not used with
great care.
To protect the surface of the molten Argentium for casting - if
boric acid is used, I recommend a heavy/dense coverage, however, care
should be taken when pouring, not to entrap the flux within the cast
metal. A dense layer of small graphite or charcoal chips is another
method of protecting the melt - my maxim is… if you can see the
surface of the metal, so can the oxygen. A small graphite rod can be
used to occasionally part the cover to observe the colour of the
molten metal.
Is is important not to overheat Argentium Sterling Silver. Remember
that Argentium does not show the darker red glow/colour of standard
sterling silver when molten/annealed. It is good practice to melt
and pour the alloy as quickly as possible and to pour Argentium at
the lowest possible temperature.
I pour my ingots into a preheated enclosed steel mould. This
produces a cast ingot where all the faces are flat and if required
they can easily be filed clean. I lightly oil the surface of the
ingot mould before heating.
Quench the ingot while it is still hot but after the red heat is no
longer visable.
Please let me know how you get on.
Peter Johns
Technical Director
Argentium Silver Co. Ltd
@Peter_G_Johns