I hate to toss cold water on your plan, but I have serious doubts about you
achieving success. You have a high enough temperature to melt stainless use
an AO torch, of that there's no doubt, but it may be hard to contain enough
of it to do you any good. I've melted platinum with an AO torch. By the
time you've melted a troy ounce, it gets difficult to keep it all molten.
Granted, it melts at a higher temperature, but not enough to make a
significant difference. The other problem you're likely to encounter is
destroying the alloy and creating gasses in the heat. It's safe to say
you'd have some serious oxidation with which you'd have to contend. In
general, I'd say the idea isn't sound, but I'd be interested in hearing from
anyone that has had success. Such materials are generally melted by
induction, where there is no direct contact of the molten metal with a
I don't know about stainless Harold, but at least 50 years ago I melted
platinum (well, 10% irridium - 90% platinum alloy) in open crucibles
using a torch running oxygen/city gas, while centrifugally casting stuff
in "lost wax" molds at my dad's jewelry manufacturing shop. The
crucibles had a nipple on one side fitting into the sprue (gate) hole in
the mold. The metal rose up the side of the crucible and flowed into the
mold when the casting machine spun.
The platinum melted at a white heat and I had to wear very dark glasses
for that job. Can't remember the total weight of the "shots", but we
usually "treed up" quite a few pieces of jewelry off one sprue so I'm
pretty sure I was melting well over an ounce each time.
I remember the molds were kept quite hot in an furnace until just before
the casting operation, to reduce chilling of the molten metal. I don't
recall the specific furnace temperature, but IIRC it was just short of a
The molten platinum was so hot it changed the "plaster" molds into a
glassy material about a millimeter thick coating every surface of the
cast pieces. That didn't happen when we were casting gold alloys.
We had to soak the pieces in hydroflouric acid (nasty stuff) for several
hours to eat away the glassified stuff. The acid didn't do anything to
Thanks for the mammaries,
My name is Jeff Wisnia and I approved this message....
To be brutally honest, I, too, used city (or "natural") gas when I melted
platinum. In my case, I was melting sponge from the refining process, in
order to end up with a button of pure platinum. The recommended fuel when
doing so is hydrogen, but I was not so equipped.
Rarely did I encounter anyone that did their own platinum casting when I
refined, and my list of customers numbered over 60. Quite a few of them
worked platinum, but didn't cast it. As I recall, there is a vertical
centrifuge used in place of a horizontal one for casting platinum.. Why,
I don't know.
Not only are the molds kept hot, but the recommended investment used is
different from that used for gold and silver alloys.
Makes me wonder if, perhaps, you may have been using the gold investment,
although I never witnessed any of the castings as they came from the molds
when the recommended investment is used. . Could be that the proper
investment does that as well. Dunno.
I, too, had to pickle my button (which I still have after all those years)
even though it was melted in the proper melting dish. The problem with
platinum is that it melts at the same, or very near the same temperature as
silica, which is used to make the dishes. It's difficult to melt the
platinum and not get some of the silica involved.
Yep, sort of a nice walk down memory lane for me, too. I sold the refining
business more than ten years ago. Don't miss it!
You can melt and weld stainless steel with an oxy-acet torch, but it
To achieve a molten puddle you have to use a carburizing flame.
The carbon feather should be about 3-4 times as long as the inner cone.
The problem with this is that is imparts carbon into the stainless
steel, which can bond with the chromium to form chromium carbides,
which cause cracking in stainless steel welds and can also be a seed
So it can be done, bu it has risks.
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