There are many types of secondary refining equipment.
The VD/VOD (Vacuum Refining Furnace) makes steel smelting in vacuum environment, with argon blowing throughout the entire process, reduces the partial pressure of impurity gas in molten steel, thus reduces the content of hydrogen, oxygen, and nitrogen in molten steel and improves the quality of molten steel. Besides, blowing oxygen into the molten steel in vacuum environment can reduce the carbon content in molten steel and maximumly ensure that the chromium in molten steel is not oxidized. Basing on the structure type, it includes two types: tank cover type and tank car type, with furnace tonnage ranging from 10 tons to 160 tons.
AOD (full name: Argon Oxygen Decarburization) is the abbreviation of the argon oxygen decarburization refining method. It blows oxygen to the molten steel to decarburize under normal pressure, simultaneously blows argon (or nitrogen) to reduce the CO partial pressure during decarburization, thus achieves carbon removal and chromium preservation at reasonable temperature. It is mostly used for the refining of highchromium stainless steel, with furnace tonnage ranging from 10 tons to 90 tons.
