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Brittle argentium castings


#1

Hi Orchid, I’ve been casting some of my filligree designs using the
Argentium 935 pro grain and have noticed some brittleness. I often
form and or forge my designs to some degree after casting and the
brittleness usually appears when forming as a crack in the piece.
When possible I fix the problem by sawing through the crack and
soldering it with hard solder. What I’m wondering is how to prevent
this brittleness in the first place. Sincemy designs are fairly
intricate I cast at flask temps at around 1100-1150Fand the metal at
1850-1880, quite hot but still within the suggested range for this
alloy. I use a ratio of around 70% fresh grain to 30% Argentium wire
scrap and reject castings. Even when using a higher percentage of
freshgrain I have still encountered this brittleness. Otherwise I
love this alloy, I never have fill problems or porosity and the
metal comes out super bright as long as I burn the flask out well and
use mostly fresh grain. Thanks for your thoughts on the matter.

Douglas


#2

Douglas,

All that you are doing is fine however you don’t mention quenching
the flask. If you are quenching as you do SS then there is your
problem. Let the flask cool down then submerge it in water and let
it soak then dig out the investment from the flask.

Vasken


#3

Hi Douglas and Orchid. I got some in person from Rio
Grande’scasting master. When Rio Grande casts Argentium 935-Pro for
tiny filigree items here is what goes on. Casting temp is 1820F,
this is considered almost too hot. The flask is 1100F and also
considered a little hot, these parameters are used in special cases
and not the norm. Wait 15 minutes before quenching. Rio Grande uses
70% to 100% fresh casting grain. The 30% of sprues, tree material
and old castings MUST be cleaned or you will experience brittle
casts. Here is what Rio Grande does to clean it. Put all sprue parts
in a barrel tumbler with burnishing compound. Tumble them just with
the parts no media, run until the parts are clean of oxides and
investment. One note on the wire scraps you are using as part of
your 30% scrap. The wire is designed to be wire and in most casting
situations wire is considered clean scrap and no issues at all would
be considered. In the caseof Argentium 935-Pro I would use the tree
and sprue parts only. 935-Pro is a designed casting alloy for good
flow and fill. The wire may be diluting the intention of the alloy,
it’s not a huge issue but I would leave that out of the equation in
this case.

Hope this helps

Sessin Durgham
Rio Grande
Technical Support


#4

I quench the flasks after the button has stopped glowing in a
darkened room. usually about 20-30 minutes after casting. Thanks
again, Douglas


#5

I’ve been casting some of my filligree designs using the Argentium
935 pro grain and have noticed some brittleness. I often form and or
forge my designs to some degree after casting and the brittleness
usually appears when forming as a crack in the piece.

Most casting alloys contain silicon to assist their casting
properties, this will make them prone to crack if they are worked
exactly like a wrought alloy. If all the normal casting parameters
are correct, 935 Pro will forge successfully. However because it
also contains silicon, it may require annealing more often than you
would when forging standard sheet and wire.

Peter