Does anyone know any sites for home casting of stainless steel? The usual
suspects are mostly about casting aluminium.
I particularly want to know what crucible material to use. Will be in a
Hi Ernie, how's the hand?
That sounds like just exactly what I want, thanks.
It doesn't seem to be that hard to do at home though, just needs a suitable
furnace*, and something to make the ceramic shells** out of.
Am I missing something?
--
Peter Fairbrother
*perhaps even a converted microwave oven furnace, I only want to cast small
Do a search on investment casting. There might be some home sites on it.
Not the easiest method of casting, requires a wax original and then
is coated with a ceramic slurry and left to dry, then dipped in the
slurry again and coated with fine ceramic sand. Repeat with slurry and
larger grit until desired thickness. Bake out wax in an autoclave. set
aside until ready to do your casting. Pre-heat mold to same temp as
metal will be for seveal hours. Melt you SS in either a controled
atmosphere furnace or an induction furnace, remove molds from oven and
pour. Easy as pie :-)
Ernie Leimkuhler wrote:
What's the difference between ceramic shell casting and investment casting?
What I had in mind was making a wax, spruing it, and adding a wax crucible
on top. Dipping the whole in slurry, then refractory flour/sand, repeating.
Dry shell. Heat shell to melt out wax, heat shell in air, red hot, till
strong and clean. Cool a bit.
Add broken metal to the crucible part, put the shell + metal in vacuum
furnace, heat the whole thing past the metal melting point. When hot enough,
pressurise the crucible top with argon (the metal will have melted into the
mould by this time, and the argon pressure will act on the molten surface,
which should be halfway up the sprue at this point, pressing the molten
metal into any remaining crevices of the mould). Switch the furnace off, and
cool.
This is a bit unlike the normal investment casting process, in that all the
metal stays molten inside the shell rather than forming a solid skin on the
outside as soon as it is cast (the shell usually being cooler than the metal
in investment casting, eg shell 1100 C, metal 1500 C, at the moment of
casting). In this case both the shell and the metal would be at ~1500 C, and
the metal could flow slowly into place rather than a fast casting.
Anyone forsee any difficult problems?
I have vacuum, and argon, and 240 Volts as I am in the UK. I can do the
waxes myself, I hope and expect.
As I see it the two areas of uncertainty are the investment/ceramic shell
material, and the furnace (I am thinking of modifying a {pair of} microwave
oven, or an induction ring from an electric kitchen hob, or perhaps both.
I can't afford the £1,000's+ for a ready-made 1500C electric furnace). Any
ideas, comments?
Ceramic Shell requires a bigger investment. :)
[And I don't think regular investment will take the temp you need]
The wax expands as it heats, before it melts and frequenlty [In my
limited experience] results in cracks in the investment. The metal
will exert a fair amount of pressure towards the bottom of the shell.
Your metal and the silica will be in contact for a relatively long
time, I would worry about possible reactions forming a skin.
Peter,
You should look into the Jewelry industry. Investment (or "Lost-Wax")
casting is used by jewelers to make rings, etc. mostly in Silver and Gold,
but they also make them in Platinum
(which has a higher melting point than Stainless). They use the flask method
(which works well for small pieces) with centrifugal or vacuum casting
machines. Here's just one of many sites to tell you a bit about this:
http://jewelrymaking.about.com/library/blcast.htm
There are companies dedicated to selling investment material, injectable
wax, casting machines, induction furnaces, etc. for small investment
castings by jewelers. There are casting machines and furnaces dedicated to
do Platinum casting (which can be adapted to Stainless). Here are a few of
the main players:
http://shorinternational.com/casting.htm
http://www.kerrlab.com/jewelry/index.cfm
http://www.gesswein.com /
Hope this helps.
Regards,
Alex P.
Check into what goes on in the dental laboratory industry. The alloys
that go into many partial denture castings are in the family known as
stellites. They are cast day in and day out in dental laboratories.
Mostly, they melt the alloys by induction but an oxyacetylene torch will
do well in a pinch.
bob g.
James H. wrote:
The reason why usual sites are about casting aluminum (and not stainless
steel) is because you need an induction furnace to melt the stainless and
few if any home foundries would have that type of equipment.
What type of furnace do you have (pounds size, kW rating, high medium
frequency, etc.). What type of stainless steel do you intend to melt?
Your crucible supplier would be able to help you select the right type
crucible. The choices are usually Magnesite, Spinel, Alumina, Zircon and
Silica.
I always had best results with Silica crucibles when melting 316S stainless.
We were casting into shell molds, about 75-100 pound pour weight.
Mark
I don't have a furnace for metal casting. I will buy one, or make one from a
microwave oven or perhaps an induction cooker. Any advice?
The casting (singular, I want to cast one at a time) will weigh at most a
hundred and fifty grams/ 6 ounces. It will have lots of undercuts, but won't
be very large, say 60mm/ 2 1/2 inches in any dimension maximum.
304/316. It's for the impellors and casing of a small liquid oxygen/kerosene
turbopump for model rocketry.
Perhaps 321 for non-rotating parts of the turbine, and inconel 718 for the
turbine wheel. I'll probably buy the turbine wheel ready-made though.
About 1450 C max melting point, 1500 C/ 2700 F max casting temperature.
Any idea what the shells were made of? I'm thinking alumina with a silica
sol binder, any comments? Do I need zirconia?
Thanks,
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