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Hydrogen/nitrogen as a heat source?

Aloha to all Ochidians,

We cast gold or silver using propane/oxygen with a torch. We are
interested in switching over to a hydrogen/nitrogen mixture (forming
gas) as our heat source replacing our propane to get a hotter and
cleaner flame.

Can anyone elaborate on this forming gas. Why nitrogen? What’s wrong
with using just pure hydrogen? Are special regulators needed?

Thanks in advance for your help…

Steve in Hawaii

Steve, I am a small time self taught caster. I was having problems
with my acetylene/oxygen torch. Many bad castings. I called Precious
Metals West (I think…it was them) because in their ad they offer
to help solve casting problems. They told me they use
hydrogen/oxygen. I went down to my local welding supply and switched
using my same torch that I’d used for acetylene to hydrogen. So now
I use hydrogen/oxygen. No nitrogen mixed in though.I did need a much
bigger more expensive regulator but the folks at the welding supply
had one sitting around and simply lent it to me. I pay a small
amount of rent on it each year. I really like it. It’s very hot and
clean. The flame is hard to see at first but I got used to it. I
just typed in and they appeared on my
screen. Try their tech support and maybe they can give you info.

Forming gas is 95% Nitrogen , 5% hydrogen . It is not combustible.
It has the maximum Hydrogen content that will not burn in air as
such it is not a fuel gas. It is used in furnace applications to
form a safe reducing atmosphere to Protect metals from oxidizing .
It can be used for bright annealing , furnace brazing, and in
automatic casting machines As well as well as an atmosphere in
making float ( sheet ) glass. To really clean up oxides a higher
Hydrogen content is better.

Hydrogen is a good clean fuel gas but it does have some safety
concerns. It has a very broad combustible range. It does not emit
energy in the infra red range— The flame is colorless and ideally
is invisible. Color is from contamination. The gas is not stenched
and you can not smell it. Heat (fire effect) is only where the
flame is although you can feel infra red radiation from a heated
object. Jesse

i do production casting small scale, 500-1000 pieces of sterling per
week, 10-20 pieces of gold . 10 years of wholesale manufacturing. i
use oxy-acetelyene, kerr long arm centrifical, i cast 250-350 grams
per flask. i have had problems over the years, but porosity was never
the problem. seems like there is a tendency for the inexperienced to
worst case senerio avoid a problem you heard about but have not
experienced, throw money at it hoping to avoid the learning curve.
one of the problems i had, cracking of ring shanks right where the
sprue attached, i called precious metals west, swest, kerr, rio
grande, i sent samples even. no one diagnosed my problem. no one
suggested i was casting at too high a temperature. i have a
kilnminder and pyrometer. they all asked what the flask temp was,but
i was told sprue attachment, type of gas, metal temp, quench time.
one day out of frustration i called sunwest silver and was fortunate
to be able to talk to one of the casters, he suggested lowering my
flask temp, the one thing i had been paranoid to do, fear of little
pieces not filling out. 50 degrees made the difference. problem gone
not returned, happy, happy, happy. hydrogen melts faster, is cleaner,
and costs much more. richard in denver, hope to see you at snag
conference here in june!