Melting challenge after Inquarting

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Wiehan

Member
Joined
Dec 7, 2020
Messages
7
Good day

I've recently inquarted two batches of metal and recovered a very dark "coffee roast" coloured sponge. Quick scan with XRF indicated about 99.2% purity, although this was just done to get an indication of purity. Upon melting, however, the sponge took very long to melt and I struggled to pour/cast it into an ingot. I did not take the sponge into AR after the inquartation, only rinsed with hot water a good couple of times and dried before melting.
Any explanations as to why the melt would struggle?
 
Good day

I've recently inquarted two batches of metal and recovered a very dark "coffee roast" coloured sponge. Quick scan with XRF indicated about 99.2% purity, although this was just done to get an indication of purity. Upon melting, however, the sponge took very long to melt and I struggled to pour/cast it into an ingot. I did not take the sponge into AR after the inquartation, only rinsed with hot water a good couple of times and dried before melting.
Any explanations as to why the melt would struggle?
After inquarting it is parting in Nitric and when that is done it will have to be refined.
The inquarting and parting is not refining but recovery.
What and how did you try to melt it?
 
After inquarting it is parting in Nitric and when that is done it will have to be refined.
The inquarting and parting is not refining but recovery.
What and how did you try to melt it?
Thanks for your reply.

My idea with the parting in Nitric is to increase the purity of low grade metal to above 95% before refining it in an electrolytic cell.
After the parting in Nitric acid, I tried to melt the recovered metal into an anode plate in an induction melter, but really struggled to get the +/- 550g melted. I'm trying to understand why.
 
Thanks for your reply.

My idea with the parting in Nitric is to increase the purity of low grade metal to above 95% before refining it in an electrolytic cell.
After the parting in Nitric acid, I tried to melt the recovered metal into an anode plate in an induction melter, but really struggled to get the +/- 550g melted. I'm trying to understand why.
might there be a metal with a higher melting point that is not susceptible to nitric acid? Even a small amount of such impurity would raise its melting temperature.
 
Thanks for your reply.

My idea with the parting in Nitric is to increase the purity of low grade metal to above 95% before refining it in an electrolytic cell.
After the parting in Nitric acid, I tried to melt the recovered metal into an anode plate in an induction melter, but really struggled to get the +/- 550g melted. I'm trying to understand why.
What is your feed stock?
 
Thanks for your reply.

My idea with the parting in Nitric is to increase the purity of low grade metal to above 95% before refining it in an electrolytic cell.
After the parting in Nitric acid, I tried to melt the recovered metal into an anode plate in an induction melter, but really struggled to get the +/- 550g melted. I'm trying to understand why.
What kind of induction melter do you have?
 
might there be a metal with a higher melting point that is not susceptible to nitric acid? Even a small amount of such impurity would raise its melting temperature.
Thanks for your input. I was thinking along the same lines ...
 
Feedstock is mix of 9 & 14k old gold jewelry.
15kW water-cooled induction melter, using graphite crucibles.
did you inquart with silver?
If so most of the potential candidates of high melting elements should have been helped into the solution.
If you used copper I do not think it has the same effect as Ag on PGM's to make them more susceptible to nitric acid digestion.
 
Feedstock is mix of 9 & 14k old gold jewelry.
15kW water-cooled induction melter, using graphite crucibles.
Maybe too much mass, and to little insulation along with not enough heel.
The graphite crucible should give enough heat transfer as long as it is not cooling too much.
How about using a normal clay or alumina crucible and proper insulation with for instance kaowool.
Compress it or put some solid Gold in there so you have a proper heel to start melting.
If you have powder in an induction furnace you need very high frequencies to start melting it.
 
Thanks for your reply.

My idea with the parting in Nitric is to increase the purity of low grade metal to above 95% before refining it in an electrolytic cell.
After the parting in Nitric acid, I tried to melt the recovered metal into an anode plate in an induction melter, but really struggled to get the +/- 550g melted. I'm trying to understand why.
If I may I recently had struggles with melting a silver alloy . Looking back I honestly believe I didn’t rinse well the acid out enough. the first trial batch I had 3-4 rinses until it was what I thought clear. The second test batch I rinsed and boiled maybe six times plus another rinse just to be sure. No problems with the second batch .
Did the alloy have an acidic smell , or an unusual flux or slag ?
 
Feedstock is mix of 9 & 14k old gold jewelry.
15kW water-cooled induction melter, using graphite crucibles.
What else did the XRF shown ? With induction furnance you can sublime even that graphite crucible, so thinking about hard to melt stuff is strange. Moreover, if you had any oxide/salts contamination, all common metals, even iron would be reduced upon contact with graphite. One thing that does not add well to melting metals is carbon dust. I don´t know from where it could possibly enter the feedstock, but my head cannot imagine anything else.

What was the temperature ? What colour does the crucible glow ? Yellow ? White ? It can also be that you had some strange impurity which wasn´t affected by graphite reducing power and high melting point. I would use some flux to help it - firstly borax, then I would move to harsher fluxes.

Thing is, if the XRF did not get it (assuming on PM mode), it isn´t common metal/precious metal/base metal. So some inorganic stuff in my opinion is a possibility, hence I do not know from where it appeared in the melt in the first place.
 
What else did the XRF shown ? With induction furnance you can sublime even that graphite crucible, so thinking about hard to melt stuff is strange. Moreover, if you had any oxide/salts contamination, all common metals, even iron would be reduced upon contact with graphite. One thing that does not add well to melting metals is carbon dust. I don´t know from where it could possibly enter the feedstock, but my head cannot imagine anything else.

What was the temperature ? What colour does the crucible glow ? Yellow ? White ? It can also be that you had some strange impurity which wasn´t affected by graphite reducing power and high melting point. I would use some flux to help it - firstly borax, then I would move to harsher fluxes.

Thing is, if the XRF did not get it (assuming on PM mode), it isn´t common metal/precious metal/base metal. So some inorganic stuff in my opinion is a possibility, hence I do not know from where it appeared in the melt in the first place.
I think the clue here is eddy currents do not get strong enough because the grains are too small, so it never forms a heel that can affect the rest of the volume.
Which was my reasoning for either put in a button or compress a small fraction to form a solid block.
The frequency might not get high enough to melt the grains.
 
I think the clue here is eddy currents do not get strong enough because the grains are too small, so it never forms a heel that can affect the rest of the volume.
Which was my reasoning for either put in a button or compress a small fraction to form a solid block.
The frequency might not get high enough to melt the grains.
induction heats the graphite better than gold :)
 
induction heats the graphite better than gold :)
Yes that puzzled me, since it is an excellent way of transferring the heat.
I think a proper refine, will make it easier in case there is a layer protecting the grains.
Anyway the color of the heated vessel may give some clues.
 
Good day

I've recently inquarted two batches of metal and recovered a very dark "coffee roast" coloured sponge. Quick scan with XRF indicated about 99.2% purity, although this was just done to get an indication of purity. Upon melting, however, the sponge took very long to melt and I struggled to pour/cast it into an ingot. I did not take the sponge into AR after the inquartation, only rinsed with hot water a good couple of times and dried before melting.
Any explanations as to why the melt would struggle?
My only question is that you stated you attained a purity of 99.2% metal. What metal was the 99.2%, since you didn't state what it is?
 
You could get any blob of metal to get at a high temperature and act as a collector metal, I have no idea if you can melt it in that stage.
Note borax will eat away your crucible and will lower it's life span.
 
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