Argon Oxygen Decarburization Process Apr28

Argon Oxygen Decarburization Process...

Argon Oxygen Decarburization Process Argon oxygen decarburization (AOD) is a process primarily used in production of stainless steel and other high grade alloys such as silicon steels, tool steels, nickel-base alloys and cobalt-base alloys with oxidizable elements such as chromium and aluminum. AOD was invented in 1954 by the Lindé division of The Union Carbide Corporation, which became Praxair in 1992. An AOD converter is shown in Fig 1. Fig 1 AOD converter Today, over 75 % of the world’s stainless steel is made using the AOD process. The process is very popular because it combines higher metallic yields with lower material costs. It provides an economical way to produce stainless steel with a minimum loss of precious elements. It is part of a duplex process in which scrap or virgin raw materials are first melted in an electric arc furnace (EAF) or induction furnace (IF). The molten metal is then decarburized and refined in an AOD converter to less than 0.05 % carbon. The key feature in the AOD converter is that oxygen for decarburization is mixed with inert gas such as argon or nitrogen and injected through submerged tuyeres. This argon dilution of oxygen minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. Other benefits of AOD process include pinpoint accuracy in chemistry control down to 0.01 % carbon and lower, rapid desulfurization to less than 0.001 %, and lead removal to less than 0.001 %. The end result is a cleaner metal coupled with increased productivity. AOD process uses dilution technique for the decarburization of steel bath. The injection of inert gas (argon or nitrogen) lowers the partial pressure of CO in the bath, thus allowing  higher chromium content to be in equilibrium with lower carbon contents. The amount...