VOD (Vacuum Oxygen Decarburizaton) is a process for refinement of stainless steel through reduction of carbon content under vacuum.
The proces is based on oxidation of carbon which has to be reduced below 0.1 wt.% for better corrosion resistance of stainless steels.
Molten steel is transferred from EAF into a separate vessel where it is heated by electric current and stirred with argon inert gas. Oxygen is blown on the top of steel in the vacuum chamber. Carbon is oxidized and carbon monoxide/dioxide is formed. Gases as nitrogen, hydrogen, oxygen and carbon monoxide/dioxide are drained out of the vessel with vacuum pumps. Thermodynamical laws under vacuum allow that chromium is not oxidized or very small amounts go into slag as Cr₂O₃. This makes the VOD process a very good choice for the production of high-chromium steels with low carbon content.