SOLIDUS is highest temperature where metal is solid. Cross this
line and piece is destroyed. It may look almost the same, but high
degree of polishing no longer possible, low resistance to
deformation, and a lot of other problems.
I haven’t much experience of fusing Argentium, but perhaps somebody
here who does can comment on whether or not they notice any
problems. I haven’t. (Obviously fusing Argentium involves heating it
into the plastic range).
HEAT CAPACITY measured in how many KJ (kilo joules ) takes to
raise temperature of 1 kilogram of metal by 1 degree of Celsius.
Characteristic is important because the higher heat capacity is,
the greater temperature control is possible. Sterling - 0.2448,
Argentium - 0.2439 The difference looks deceptively small. But if
one considers that we work with pieces weighing grams, as opposed
to kilograms, the difference is significant. It makes possibility
crossing over solidus line even more likely.
I don’t follow this: as you reduce the mass of the object being
worked, the difference in the heat capacity of the work should be
reduced by the same proportion. Do you notice the difference in heat
capacity of a 1g piece of silver and one that weighs 4 milligrams
less?
The difference in thermal conductivity of the silver is far greater
and far more significant - and would have much the same effect,
effectively making the piece seem to have a lower heat capacity as
you are only heating a smaller part of it. Personally, I see this as
an useful characteristic; I guess it could either help or hinder
depending on what you were making.
Ductility and Work Hardening: Fully annealed sterling hardness -
66 to 76 DPH ( Vickers ), Argentium - 50 to 70 DPH Fully annealed
argentium is softer, but look what happens when we start working
it. 1/4 work hardened sterling - 78 to 88 DPH, while Argentium
jumps to 90 to 105 1/2 work hardened sterling - 90 to 100 DPH,
while Argentium is at 106 to 120 3/4 work hardened sterling 102 to
114 DPH, while Argentium is 121 to 135 and at full sterling is 116
to 130, and Argentium 136 to 148.
These numbers mean that Argentium requires annealing two times as
often as sterling. Margin of error in bending and forming is
shrinking. Forging times grows exponentially, and so on. This
property is the most troublesome in setting. Thin bezels reach 3/4
to ful hardness surprisingly fast. It means that if bezel is not
closed on first try, you are screwed, and setting any king of
angular stone becomes very problematic.
No, what these numbers actually mean is that Argentium can be
hardened to a greater extent than ordinary Sterling. It doesn’t
necessarily say anything about the degree of deformation that can
take place before you reach the end-point of work-hardening and have
to anneal again. And this is greater for Argentium than for Sterling.
Though, as the Argentium ultimately hardens more than the Sterling,
if you have lots of experience with Sterling you may presumably feel
that you’ve reached this limit before you actually have.
Most of what I do in silver (horn mouthpieces) involves forming
silver round a mandrel and when I switched to Argentium early on, the
process did become noticeably easier.
Have a look at the Erichson cupping test and example candlesticks in
the following link to see how much more deformable Argentium is than
Sterling:
http://www.ganoksin.com/gnkurl/r
Sterling - 1450 F, Argentium - 1410 F. Considering that Argentium
hard solder flows at 1450 F - it mean no hard solder should be
used. Argentium medium solder flows at 1378 F, only 32 degrees
below solidus.
I have heard it suggested that Argentium ‘medium’ solder should
actually have been called ‘hard’ and that the ‘hard’ solder should
have been called ‘extra hard’. And so on. I tend to go by this rule
when choosing solders for my hobby (musical instrument parts).
I was quite jumpy about using medium solder the first time, as I was
soldering 0.3-0.5mm sheet edge to edge to make what was effectively
20mm diameter seamed tubing - I was scared of melting the edges of
the sheet. It does sometimes slump slightly, but in my experience you
have to be quite heavy-handed to actually melt it. After all, the
melting range of Argentium is slightly wider than for Sterling.
Argentium is a different alloy from Sterling, and as such working
with it is noticeably different - in many ways easier, and in some
ways harder. However most of your theoretical based concerns are
unfounded. With my scientist hat on, when theory and observation
don’t match up, I tend to argue for changing the theory - or at least
re-examining my understanding of it.
Kit
