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Fire Scale & Gas


#1
is 'forming gas' like an inert gas to replace our atmospere
while your memco induction melts?

Hi Geo. I Have neglected to answered your question about forming
gas, sorry. My forming gas is a mixture of 75% Nitrogen and 25%
Hydrogen. Your gas company will mix any ratio you like. Yes, the
Nitrogen displaces regular atmosphere. The Hydrogen acts like the
old computer game “Pac-Man” gobbling up any residual oxygen
molecules. The combination works pretty well. I’ve heard of some
people using a controled “flood” of forming gas at the mouth of
flask when using a static vac pour from a crucible. However, even
if you have a completely sealed casting environment exchanged
with forming or argon gas, you still can’t get past the sulfate
content in the investment. This is where United came in with
their #57 alloy for sterling. Other companies are working on a
similar alloy. Basically they want to replace the copper in the
sterling with other constituants to bypass the copper sulfate
problem (fire scale). I cast a wide variety of sterling goods for
many designers. I need consistent results from a reliable
product. The majority of my customers want regular 'ol sterling.
I have tried United’s product and found it quite satsfactory.
But, I am a Loyal Stern-Leach customer. Their clean cosistant
product is worth my patronage. Their metalurgists are working on
a new version along the same lines. I am cautious, not by
nature, but by trial and error. I’ll try it when it comes out,
let some of my customers comment about some trial pieces before I
think about a switch. J.A.