Hello fellow GRF members,
Being new to the world of metals refining , i had no idea where to start and finding this Forum was a blessing. This forum is literally a Gold Mine! Special Mention and Thanks to lazersteve and Harold_v!!
i am currently in the process of fine-tuning the casting operations at work and was looking for guidance and pointers in the Casting department.
i am currently using a 5kg induction furnace with graphite crucible.
i usually cast 700gm ingot bars in a open mould made out of Cast Iron.
i use a Silicone mould release spray to lubricate the mould before each pouring.
i also make sure i pour under a reducing flame with LPG Gas(butane+propane)
I use Ammonium Chloride & Borax as flux,if needed.
I've had all kinds of problems , i thought i would organise all my doubts and post them in one go! :
Is it necessary to have a flame over the crucible while the gold melts?i read that this prevents the metals from being oxidised(esp Silver), however I've had people tell me that it is unnecessary. i tried it and could not find any improvements in the casting.I am just learning that silver and gold behave differently, could someone explain?
After the gold has been throughly melted, the crucible is carried over to the casting tray where the mould is kept,i find that streaks of oxidised gold forms on the molten mirror like surface of the gold while it is being carried to the mould.this in turn flows out and come on top of the ingot,pictures are attached below….is this oxidised gold? or is it due to some sort of chemical lingering on from the AR process? I've been doing all sorts of things to get rid of it, any suggestions on eliminating this streak/stain ??
I have come to realise that controlled cooling is very much important to get a mirror like surface finish on the bars, I'm in the process of devising a cooling plate for this. is it worth getting a cooling plate? and could i get any tips on how to improve surface finish and reduce casting defects like Rings and piping ?
After the ingot has been casted , i quench it in a tub of ammonium chloride solution and then water, is this advisable ? is there a better method of doing it ? this has been the age old practice of the company i work for.
While casting 9999 electrolytic silver, even though i cast it under a reducing flame .sometimes i get these black scabs forming on the surface of the bars(pics Below), what are they ?any remedies ?
I am just starting to learn about casting - any sort of ideas, suggestions,criticisms are welcomed.
thanks,
youngling
moderator please feel free to edit my post as you deem necessary.
Being new to the world of metals refining , i had no idea where to start and finding this Forum was a blessing. This forum is literally a Gold Mine! Special Mention and Thanks to lazersteve and Harold_v!!
i am currently in the process of fine-tuning the casting operations at work and was looking for guidance and pointers in the Casting department.
i am currently using a 5kg induction furnace with graphite crucible.
i usually cast 700gm ingot bars in a open mould made out of Cast Iron.
i use a Silicone mould release spray to lubricate the mould before each pouring.
i also make sure i pour under a reducing flame with LPG Gas(butane+propane)
I use Ammonium Chloride & Borax as flux,if needed.
I've had all kinds of problems , i thought i would organise all my doubts and post them in one go! :
Is it necessary to have a flame over the crucible while the gold melts?i read that this prevents the metals from being oxidised(esp Silver), however I've had people tell me that it is unnecessary. i tried it and could not find any improvements in the casting.I am just learning that silver and gold behave differently, could someone explain?
After the gold has been throughly melted, the crucible is carried over to the casting tray where the mould is kept,i find that streaks of oxidised gold forms on the molten mirror like surface of the gold while it is being carried to the mould.this in turn flows out and come on top of the ingot,pictures are attached below….is this oxidised gold? or is it due to some sort of chemical lingering on from the AR process? I've been doing all sorts of things to get rid of it, any suggestions on eliminating this streak/stain ??
I have come to realise that controlled cooling is very much important to get a mirror like surface finish on the bars, I'm in the process of devising a cooling plate for this. is it worth getting a cooling plate? and could i get any tips on how to improve surface finish and reduce casting defects like Rings and piping ?
After the ingot has been casted , i quench it in a tub of ammonium chloride solution and then water, is this advisable ? is there a better method of doing it ? this has been the age old practice of the company i work for.
While casting 9999 electrolytic silver, even though i cast it under a reducing flame .sometimes i get these black scabs forming on the surface of the bars(pics Below), what are they ?any remedies ?
I am just starting to learn about casting - any sort of ideas, suggestions,criticisms are welcomed.
thanks,
youngling
moderator please feel free to edit my post as you deem necessary.