4. VOD process

In the VOD process, also known as "ASV" (vacuum refining), the molten alloy is treated in a vacuum. This results in very low CO partial pressures; the vessel pressure could be lowered to 100 hPa during decarburization.

Decarburization is performed by injecting oxygen through a lance, while a small amount of inert gas (argon) is injected through single nozzles located at the base of the vessel (figure 9 ).

While the VOD process is well suited to the production of special stainless steels (ferritic grades with high chromium content (Cr ≈ 30%), austenoferritic grades (duplex) and certain superaustenitic grades), its technical and economic performance is less attractive than that of the AOD process for the majority of stainless...