I just stumbled across this site. As a metallurgist in industrial investment casting foundry, I have a couple of thoughts. Temperatures for castings should be around 2800F for good flow. the thinner a section, the more heat you need to keep it from freezing off too soon. Also, stainless steel is a mushy freezer, more prone to shrinkage porosity than bronze. (I haven't worked with Al).
I don't think grain size will be a factor for machining castings. SS is gummy, so tends to wear cutters faster.
I agree that induction melting is better than cupola. I don't know much about cupolas: doesn't it work by burning carbon, so are mainly used for cast iron? If so, then that it going to change the composition of your SS if it is in direct contact with the carbon. 316 stainless is supposed to be low carbon. Some bad things can happen to 316, as far as carbides in the grain boundaries, and how it can react to heat treating.
No matter how much you shield, you will not be able to overcome h20 and excess oxygen in a combustion system. In induction heating, you can shield by a liquid nitrogen drip, or flowing gaseous Nitrogen over the melt, and keeping a lid on it as much as possible. You need to make sure you have good ventilation.
melting stainless steel in a cupola
I just stumbled across this site. As a metallurgist in industrial investment casting foundry, I have a couple of thoughts. Temperatures for castings should be around 2800F for good flow. the thinner a section, the more heat you need to keep it from freezing off too soon. Also, stainless steel is a mushy freezer, more prone to shrinkage porosity than bronze. (I haven't worked with Al).
I don't think grain size will be a factor for machining castings. SS is gummy, so tends to wear cutters faster.
I agree that induction melting is better than cupola. I don't know much about cupolas: doesn't it work by burning carbon, so are mainly used for cast iron? If so, then that it going to change the composition of your SS if it is in direct contact with the carbon. 316 stainless is supposed to be low carbon. Some bad things can happen to 316, as far as carbides in the grain boundaries, and how it can react to heat treating.
No matter how much you shield, you will not be able to overcome h20 and excess oxygen in a combustion system. In induction heating, you can shield by a liquid nitrogen drip, or flowing gaseous Nitrogen over the melt, and keeping a lid on it as much as possible. You need to make sure you have good ventilation.