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Making sterling alloy/casting


#1

Hi.

I had posted a message earlier.Hope for a response this time.

I am casting on continuous caster to make billets for sheet
rolling.

As I make the sterling in the caster crucible I need accurate
mixing.I have effective nitrogen purging thru the crucible and
the die also.

Do I add the fine silver first for melt and then add copper or
reverse the order. The problem is that continuous caster
crucibles have a dead space cavity yet I need mixing to sterling
accuracy?

The last experiment I added copper first and the assay was not
uniform.

Please respond.

Rajah.

Ps I have another unanswered query on sheet rolling which I will
post again and sincerely hope for a response this time…thanks
in advance.


#2
   As I make the sterling in the caster crucible I need
accurate mixing. I have effective nitrogen purging thru the
crucible and the die also.

Nitrogen is not realy inert you may want to use Argon instead
you will see a difference in the metal as it comes out of the
caster. You may also want to use forming gas (Nitrogen &
Hydrogen) as an active oxygen getter, but nitrogen by itself is
not too good.

   Do I add the fine silver first for melt and then add copper
or reverse the order. The problem is that continuous caster
crucibles have a dead space cavity yet I need mixing to
sterling accuracy?

You must alloy in a preliminarily melt (stir the melt to insure
mixing) before putting it in the continuous caster as it will
not be mixed thoroughly from a single melt

Jim


@jbin
James Binnion Metal Arts
2916 Chapman St
Oakland, CA 94601
510-436-3552


#3
  Do I add the fine silver first for melt and then add copper
or reverse the order.

Rajah, I have found it better to heat the metals with the highest
melting points first which in your case would be the copper.
Perhaps you just didnt get the metals hot enough or the mixing of
the metals was not long enough.


#4

Rajah, I have found it better to heat the metals with the highest
melting points first which in your case would be the copper.
Perhaps you just didnt get the metals hot enough or the mixing of
the metals was not long enough.

Thanks for the suggestion.I have just cast again in the wrong
order but with certian procedural modifications.Next time aroung
I will follow your suggestion and revert with the result.

Thanks Rajah


#5

Hi James.Thanks for your response.

   Nitrogen is not realy inert you may want to use Argon
instead you will see a difference in the metal as it comes out
of the caster.  You may also want to use forming gas (Nitrogen
& Hydrogen) as an active oxygen getter, but nitrogen by itself
is not too good.

Although I was using Nitrogen garunteed as 99.999, Today I cast
with Argon.Unfortunately I had no specs for oxygen content.I 'll
settle the issue with the supplier.Forming gas??if I purge the
crucible with it will not the hygrogen cause an explosion??? the
pot temperature is sterling melt temp.

You must alloy in a preliminarily melt (stir the melt to insure
mixing) before putting it in the continuous caster as it will
not be mixed thoroughly from a single melt

Will try.

The billet that emerges is dark.Is it normal? How should it
look?By the way I use a self buit horizontal caster(Copied from a
copper caster).Its an extreemly thin surface,what it is I am not
sure as it is only superficial and on the surface.Should I clean
it? How?

Thanks

Rajah


#6

Hi James and Rajah, I thought I’d butt in here with a comment on
forming gas. I use a mixture of 75% Nitrogen & 25% Hydrogen.
It’s cheaper than argon and more pro-active. I use a very small
"drip" of the forming gas, about 10-15 cfh (cubic feet an hour)
on a covered graphite crucible. If you heat the crucible first
and introduce the forming gas slowly it has no explosive action.
However, you can have your gas supplier mix a smaller amount of
Hydrogen or a percentage that works for you. J.A.