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Casting Argentium Sterling


#1

Hi,

I was wanting to cast some large objects in Argentium silver.
Does it cast as normal sterling silver or are there differences?

If yes, then any details would be gratefully received.
what are the drawbacks.

Where can I Buy Argentium from in the US and/or Australia?
how much above the spot price per kilo does it normally go for?

kind regards,
Brendan


#2

I can find a bunch about Argentium silver on Ganoksin, and other
places. But there seems to be a shortage of info about casting
Argentium silver, such as:

Casting temperature
Flask temperature
Vacuum casting guidelines
Centrifugal casting guidelines
How long to wait before quenching after casting
etc.

Any expert technical info out there?

Jon


#3

I cast Argentium Sterling regularly one to two times a week…I
am not an expert but here is what I do.

I am only casting 2 1/2 inch flasks ( all custom work, small items )

  • centrifugal casting - torch (propane & oxygen) to melt and I use a
    somewhat hotter flame than I use for regular silver (for regular
    silver the flame I use is somewhat reducing, I use more oxygen in the
    flame when casting Argentium) The usual amount I cast is from 10 to
    40
    grams in a flask

i) I find that I need a mix of new grain to old buttons of 60 % new
and 40% old (50/50 shows some signs of a poorer cast) I make very
sure the old material is very clean

ii) I coat the material to be cast with boric acid dissolved in
alcohol, then burn off the alcohol, I use no other flux

iii) I am careful to not over heat the metal ( molten Argentium looks
different from molten sterling) I cast shortly after the metal has
become fully melted

iv) the flask temperature I use is slightly higher than what I use
for regular sterling (1150f for very fine items down to 850f for
larger)

v) I always let the flask cool to about 250f - 300f or right to room
temperature and I break out the cast, I do not quench. I have
quenched hot flasks in water, the casting will crack!

vi) I ultrasonic clean off investment for a few minutes only, pickle
in hot sparex for a few minutes, then ultrasonic again about one
minute then repeat if needed I have clean white porosity free
castings
to start to work on. Castings cooled to room temperature are harder
than those broken out of a hot flask

I am looking forward to hearing from other casters to learn more.

Franklin


#4

Hi Jon,

sources for Argentium Silver info include:

My site: http://www.cynthiaeid.com
http://www.argentiumsilver.com
http://www.sternleach.com
http://www.gsgold.com
Trevor’s site: http://www.touchmetal.com/blog/argentium-blog.html
Marty Andersen’s site: http://argexp.blogspot.com/

Following are two info sheets: the AS 925 casting info sheet from
Stern-Leach, and a section from the Argentium Silver Co.'s sheet. I
think they cover all the topics you asked about, except for any
mention of vacuum casting. I can probably find out for you—what
exactly do you want to know about vacuum casting that is not covered
in the following

Cynthia Eid
http://www.cynthiaeid.com

Argentium[tm] Casting Grain

DESCRIPTION: A new tarnish and fire scale resistant casting alloy
which can be age hardened twice as much as regular sterling silver.

FORM: Argentium[tm] grain comes as roughly spherical particles
ranging from 1.75 to 4.75 mm in size.

ITEM NUMBER: G6646, G6654 (Bright Cast)

COMPOSITION: 93% Silver

DENSITY: 5.41 troy ounces/in3

SOLIDUS: 1410 F (766 C)
LIQUIDUS: 1610 F (877 C)

CASTING: When investment casting, a pour temperature of 1740-1780 F
(950-980 C) and a flask temperature below 1250 F (677 C) is
recommended. If casting without a protective atmosphere, the use of
boric acid flux or graphite powder is effective. After casting the
metal, a minimum of 15 minutes air cooling is required before
quenching. Investment may be easily removed with water spray,
ultrasound, and pickling solution.

POLISHING: To avoid contamination from other alloys in the workshop,
a separate wheel should be used for Argentium[tm] sterling only. If
this is not possible, thoroughly rake wheels before use. After
polishing, heat the castings in an air atmosphere to 250 F for 10
minutes to activate the germanium oxide layer which is highly tarnish
resistant.

HARDENING: Typical hardness of rapidly quenched pieces is 70 DPH.
Flasks cooled to room temperature can approach 110 DPH and heat
treated castings can approach 125 DPH! (Approximately twice the
hardness of standard Sterling silver!). To obtain this hardness,
place the castings in the oven at 580 F for 45 minutes.

SOLDERING: Argentium[tm] Sterling displays a lighter color when
heated. If the metal looks yellow or light orange, it is too hot. It
is important to avoid overheating this metal.

REMELTING: Remelting scrap may result in brittle castings.

Warranty Clause: Stern-Leach believes this data to be accurate and
reliable. However, these are recommenda=ADtions only given free of
charge and should be employed by you with discretion and risk.
Stern-Leach assumes no responsibility for difficulties or damages
incurred by adhering to this

Casting specs from Argentium Silver Co.:

INVESTMENT CASTING

Casting temperature range

1750-1800 F / 955-980 C. Argentium=99 Sterling Silver displays a
paler color when heated/molded, therefore the casting temperature
cannot be judged by eye.

Flask temperature

Lower flask temperatures are recommended. For guidance, drop by a
minimum of 85 F / 30 C below regular temperatures used for standard
sterling silver.

Successful castings have been made using the following flask
temperatures:

700-800 F (370-425 C) for heavy castings and 800-1000 F (425-535 C)
for light castings.

Crucibles

To avoid contamination from other alloys, it is important to use
separate crucibles for Argentium Sterling Silver. Do not use silicon
carbide crucibles.

Protective atmosphere/fluxing

A protective atmosphere is recommended when melting Argentium=99
Sterling Silver. If a protective atmosphere is not available, flux
can be used (boric acid is recommended). Skim any oxides off the
surface before stirring.

Hardness wet investment removal

Leave flasks to cool for 20-25 minutes before quenching. This will
give castings approximately the same hardness as standard sterling
silver (70HV). To raise the hardness to approximately 95HV, heat
castings at 580 F / 300 C for 30-45 minutes and air cool to room
temperature.

Hardness dry investment removal. Leave flasks to cool to room
temperature before removing castings from the investment. This will
give Argentium Sterling Silver a hardness of approximately 100HV.

Precipitation hardening

For hardness above 100HV, follow precipitation-hardening
instructions.

Re-melting

Use at least 50% fresh / 50% scrap mix. For high-quality pieces,
using more fresh metal will yield superior results. It’s important
that used trees and buttons are free from investment powder residue
to avoid contamination.