When melting any ferrous metal, (and most non-ferrous), it is common in industry to perform the melt in a controlled atmosphere. Generally, an inert gas such as argon, helium, nitrogen or carbon dioxide is maintained in the induction furnace to prevent oxidation, absorption of undesirable elements or other variables during the melt. High carbon steel is particularly prone to losing carbon through oxidation, most steels are better without excess sulfur, etc.
In a cupola-type melt, the metal is essentially subjected to open flame and thus highly prone to oxidation if the atmosphere is not maintained in a reducing state by the addition of some material to consume free oxygen. Stainless steel, generally composed of iron, nickel and chromium, is only stainless if the chromium carbides are in suspension and the surface chromium is oxidized. If tramp elements are introduced, these balances can change. Thus the use of controlled atmospheres. The need for atmosphere control necessitates isolating the melt from the flame and free atmosphere, so induction furnaces are appropriate, or muffle-type furnaces or closed crucibles.
I'm not too knowledgeable about cupola melting, so I can't say how you could control the atmosphere in one effectively. Building a cupola that will withstand for a sufficient period of time the more than 2600F temps necessary to melt stainless may be a problem, too.
Finally, your desire fora michineable final product concern me. Typically, steel is cast into ingots large enough to be rolled down to billets and then into finished form aftera reduction in section of some 85% or thereabouts. This high degree of reduction is necessary to develp the tight grain structure necessary to have a piece that is both strong and dense enough for machining.
I wish you luck with your efforts and look forward to hearing how it comes out.
Regarding the controlled
Regarding the controlled atmosphere:
When melting any ferrous metal, (and most non-ferrous), it is common in industry to perform the melt in a controlled atmosphere. Generally, an inert gas such as argon, helium, nitrogen or carbon dioxide is maintained in the induction furnace to prevent oxidation, absorption of undesirable elements or other variables during the melt. High carbon steel is particularly prone to losing carbon through oxidation, most steels are better without excess sulfur, etc.
In a cupola-type melt, the metal is essentially subjected to open flame and thus highly prone to oxidation if the atmosphere is not maintained in a reducing state by the addition of some material to consume free oxygen. Stainless steel, generally composed of iron, nickel and chromium, is only stainless if the chromium carbides are in suspension and the surface chromium is oxidized. If tramp elements are introduced, these balances can change. Thus the use of controlled atmospheres. The need for atmosphere control necessitates isolating the melt from the flame and free atmosphere, so induction furnaces are appropriate, or muffle-type furnaces or closed crucibles.
I'm not too knowledgeable about cupola melting, so I can't say how you could control the atmosphere in one effectively. Building a cupola that will withstand for a sufficient period of time the more than 2600F temps necessary to melt stainless may be a problem, too.
Finally, your desire fora michineable final product concern me. Typically, steel is cast into ingots large enough to be rolled down to billets and then into finished form aftera reduction in section of some 85% or thereabouts. This high degree of reduction is necessary to develp the tight grain structure necessary to have a piece that is both strong and dense enough for machining.
I wish you luck with your efforts and look forward to hearing how it comes out.