In Reply to: Re: Vacuum stainless steel tank posted by Silvia Johnson on 03/05/01 at 11:25 PM:
Metals can be melted in a vacuum chamber to refine them, remove gaseous impurities and eliminate oxidation of the melted product that would accur if it was melted in atmospheric pressure.
The same techniques are often used for heat treatment of metals such as stress relief and annealing. Inert gas can also be introduced after the O2 has been removed.
For a vacuum furnace mild steel would often be used rather than st steel. The chamber has heaters, crucibles and other internal components that outgas a great deal so st steel isn't needed.